Other than the setting conceit that the Imperium has the highest tech, I don't buy the rest of that at all. There are aliens that are dramatically physically superior to humans (Virushi) and aliens that are dramatically physically inferior to humans. Importantly, aliens are almost always presented as intellectualy equal to humans.You could ignore the pluses and minuses. Each new iteration of Trav makes all the species even weaker, somehow.
Zhodani may have psionics, but their TL is stagnant at TL 14 so the Imperial WASPS can have the technological superiority. Aslan, Vargr and other species are somehow lesser in some way - smaller characteristic die rolls, inferior senses - just to give the humans a sense of advantage.
No, not advantage. Supremacy.
Aslan are not inferior to humans, for instance. If you assume a straight 777 baseline for physical stats, Aslan would be 868 and have a bonus to senses and the dewclaw.
Vargr have always been a 686 physical statline. The mongoose 586 is definitely an outlier, but there's no reason to think its a vast conspiracy to make humans supreme.
The fact that three of the six major states (Imperium, Consulate, Confederacy vs the Heirate, Federation, 2k Worlds) are human is definitely also a setting conceit, but even that is largely attributed to aliens (aka the Ancients), not some human specialness. Unless you think being picked as Grandfather's favorite servants a mark of racial superiority.