Different flavor of shmeerp, essentially.
In sci-fi writing circles, there's a term called a 'shmeerp', and it's something to avoid. The saying goes - "If it looks like a rabbit, and acts like a rabbit, don't call it a shmeerp!" Basically, there's a tendency among new sci-fi (and fantasy!) authors to make up new and fancy names for whatever it is they've made when it doesn't actually matter.
And then, of course, there's an arms race among shmeerp users, because while vanilla shmeerps aren't interesting, sometimes if you make your shmeerp un-rabbit-like enough, it's actually interesting so writers keep upping the ante of shmeerp names. So first you have inter-dimensional beings, then extra-dimensional, and now there's the glorious fifth dimensional species. There are real definitions for these terms, but they aren't particularly meaningful (that is, they aren't specific in the slightest - it's like calling a human 'something which exists in the universe') but the colloquial usage in sci-fi doesn't follow them - it's just calling a rabbit a shmeerp.