Having seen it, I am fairly convinced by Gilad M's answer. However, I think the reasoning can be clarified and expanded on.
So, we start out imagining the simplest creature that could crawl out of the sea onto land and stand up. It will "want" to keep its center of mass low, and span the (hyper)plane for stability. If you zoom in on one limb attachment section of a 3D tetrapod (i.e., the shoulder girdle or hip girdle), you have the major axis of the animal (the spine) defining one dimension of the plane, and then two limbs, providing two points of contact with the ground, defining a second axis; the third point of contact with the ground is provided by something located elsewhere along the spinal axis. That third contact point can be expected to be provided by another pair of limbs, rather than a single limb, since having 4 total permits one to move while maintaining 3-point stability--thus, you end up with matched pairs of limbs. Additionally, since the pairs of limbs do not span the plane by themselves, they also serve as a rotational axis about which the spine can pivot, so 3D tetrapods can stand up. In 3D, if you add additional limbs on the same body segment, you loose the ability for the body to pivot around those limbs--see, e.g., radially symmetric creatures like seastars (flat) or sea cucumbers (elongated), or cephalopods. There is thus no way for such a creature to transition from laying with its primary body axis parallel to the ground to standing with its primary axis perpendicular to the ground.
Moving up to 4D, a primitive creature will still "want" to remain low to the ground, and span the hyperplane for stability. In order to get that static stability, we need at least four points of contact with the ground--plus one to permit movement. However, there are far more different options for how limbs might be arranged. For an axially extended creature (something with a linear spine that can lay down or stand up), it is clear that one will need at least two different limb attachment points, at opposite ends of the spine, to support the entire length of the spine; otherwise, a single limb group would have to exert a lot of torque to support a cantilevered body; one could perhaps imagine something like a 5-legged theropod with its single hip girdle in the middle and the body balanced across it, but that is both not a primitive-looking condition (nothing on our 3D world came out of the ocean balanced on a single limb girdle, despite bipedalism later evolving multiple times), and doesn't lend itself to evolving into something with distinct sets of arms and legs--i.e., it's not very good for a "human-analog". In addition, we should expect each limb girdle to have at least two limbs attached to it, just as in 3D--if there were only one, then when it was that limb's turn to move, the cantilevered body would bee unsupported, and you would end up with a 3-legged-dog situation.
If each limb girdle still has only two limbs attached, then three such girdles would be required, resulting in a six-limbed basal animal, which could raise its front limbs in a direct analog of the 3D mantoid / centauroid body plan, resulting a 4-legged, 2-armed creature. Such a creature would be less stable than a 3D centauroid, as it would not be able to span the surface with the three remaining legs while moving one, but more stable than a 3D biped.
However, it is possible for a primitive 4D tetrapod-analog to have an arbitrarily large number of limbs attached to a single limb girdle, much like radially symmetric 3D creatures, without losing the ability to hinge the spine. The reason for this hinges (pun intended) on the fact that rotations (in space of any dimensionality) do not fundamentally occur around axes, but rather in planes. The utility of linear axes to describe 3D rotations is a 3D-specific artifact of the fact that selecting a rotation plane leaves a single unique perpendicular vector left over to span the space. Radially-arranged limbs on a 4D creature, however, can span a single 2D plane with their attachment points, leaving a second plane containing the spine free to permit rotation of the spine around that set of limbs (hence the (geometric, if not evo-devo) plausibility of the aforementioned 5-legged theropod).
Thus, since we can attach three or more limbs to a single girdle, it is not in fact necessary to adopt the centaur-analog body plan with three limb girdles--which is convenient, as a 4D human-analog with only two sets of limbs is certainly more human-ish than a centauroid! In fact, we can achieve the minimum limb set for statically stable locomotion of an axially-extended creature (5 limbs grouped at least in pairs) with one three-limb set and one two-limb set. Such a creature could stand up, hinging its spin from horizontal to vertical around the 3-limb girdle, to free up 2 arms while remaining as dynamically stable on 3 legs as a 3D human is on 2. This is, geometrically at least, a perfectly plausible body plan, and results in an unusually high degree of freedom for the joint between the spine and the arm girdle. If a consistent symmetry type is to be maintained along the full length of the body, however, that would dictate a 3-leg, 3-arm arrangement, with full trilateral symmetry. This gets us to the basic body plan proposed by Gilad M.
So, to directly answer the question: No, it does not make the most sense to remain restricted to pairs of limbs, thus dictating 3 limb sets total; and yes, arbitrary numbers of limbs with high radial symmetry can in principle be supported on each limb girdle of a 4D creature.
Moving into the realm of greater speculation based on non-purely-geometric arguments, however, the 3+3 hexapod arrangement may or may not actually be optimal. After all, there are no trilaterally symmetric organisms in our world, and very few quadrilaterally symmetric ones. The larger degree of attachment available between radial segments that meet along 3D cell boundaries rather than 2D cross-sectional surfaces may significantly change whatever considerations lead Earthly evolution to favor 5+ symmetries, thus making trilaterally symmetric 4D "humans" perfectly plausible, but as this is well outside the realm of simple arguments to be made about hinging structures, how exactly that would impact 4D creature development is not nearly as obvious. Perhaps the optimal 4D human-analog is actually a ten-limbed, pentalaterally symmetric creature!