Why would a shapeshifter that shifts between a wolf-like and a human-like form necessarily have the exact senses of either a wolf or a human in those respective forms?
There are documented examples of animals having greater olfactory discrimination ability than might be expected, which if nothing else can serve as a basis for progressive evolution of such a trait. Take for example ‘Microsmatic’ Primates Revisited: Olfactory Sensitivity in the Squirrel Monkey, Laska, Seibt and Weber, 1999, emphasis mine:
Using a conditioning paradigm, the olfactory sensitivity of three squirrel monkeys to nine odorants representing different chemical classes as well as members of a homologous series of substances was investigated. The animals significantly discriminated dilutions as low as 1:10 000 n-propionic acid, 1:30 000 n-butanoic acid and n-pentanoic acid, 1:100 000 n-hexanoic acid, 1:1Mio n-heptanoic acid, 1:30 000 1-pentanol, 1:300 000 1,8-cineole, 1:1Mio n-heptanal and 1:30Mio amyl acetate from the near-odorless solvent, with single individuals scoring even slightly better. The results showed (i) the squirrel monkey to have an unexpectedly high olfactory sensitivity, which for some substances matches or even is better than that of species such as the rat or the dog, and (ii) a significant negative correlation between perceptibility in terms of olfactory detection thresholds and carbon chain length of carboxylic acids. These findings support the assumptions that olfaction may play a significant and hitherto underestimated role in the regulation of primate behavior, and that the concept of primates as primarily visual and ‘microsmatic’ animals needs to be revised.
Given that human/wolf shapeshifters might very well strictly speaking have no real taxonomic connection to either humans or wolves, and especially in the light of the shapeshifting ability to begin with, it doesn't seem too much of a stretch that their olfactory sense could be different from that of either species. Hence, you could design those senses as needed, as long as you can provide a reasonable explanation for how they got that way. (Which I think you pretty much threw out the window already with their shapeshifting ability, but that's not necessarily a reason to not try to be plausible with the remaining issues surrounding such a creature.)
As an alternative, have a look at brachycephaly in dogs. (For some examples of breeds, consider English bulldog, French bulldog, pug, Boston terrier and Pekingese. These are named in the Swedish Wikipedia article on the subject.) In order for a wolf to shapeshift into a human the muzzle must already be absorbed into the front of the head, with all of what that means, so by just a moderate amount of handwaving you could consider the face of the individual in human form to be a brachycephalic variant of that in wolf form. By merely rearranging, it should be possible to maintain at least a similar sense of smell in the two forms; same order of magnitude olfactory sensitivity, instead of several orders of magnitude difference as is the case with wolves (or dogs) and humans.