Debate fuels my Fire
Even the rabbit-folk aren't completely new to D&D. In the same supplement that gave us the hsaio (giant, intelligent owls), we got the pooka, fey shape-changers. Pooka, like rakshasa, aren't limited to a single animal form (tigers for rakshasa), but all of the illustrations and examples were of rabbit-pooka.
Yeah, for a moment here I was thinking Strixhaven is possible, but I'm back into the leaning "not happening." A whole bunch of cards have been released, and they are heavily owlfolk but really none of the other subraces.
I think this UA actually is intended for a Feywild product. Either it's a monster book (with the dragon UA) or the adventure path this year is Feywild themed. Plenty of Feywild material in D&D to get that UA to work, as you cite.