The cat was also mentioned in the first two posts of the "real leaks" leak, in the same post that mentions a bird that has appearances that differ by island (Oricorio). While the later post in that thread that "leaked" Alola forms hasn't been completely correct, there's no indication that came from the OP leaker. The first two posts have been correct or as yet unproven.
The second post is a confusing mess, but overall I believe the evidence points to it being false.
Claims the second post makes:
Flying type that's type varies by island.
Breeder cat.
Ice/Ghost snowman.
Alolan Abra has new animations (I can't remember, have we seen any of the Abra line in play?)
We have taken the flying type to be indicative of a predicted Oricorio, which is fair. But if that is true it also means the breeder cat should be true. Which leaves us with two possibilities:
1) The Split Evo's post is true, because it predates the "real leaks" leak.
2) The Split Evo's post is not true, but just happened to guess an actual gimmick of an actual Pokemon, down to its exact species. I do not consider this likely.
So your belief in the veracity of the second post of the "real leaks" post depends upon how important you find the oricorio prediction vs. how likely you find the rest of the Split Evo's post to be true.
The relevant Split Evo's post also predicted:
Lilly has a Zygarde Cell in her bag, and you get Zygarde 10% by the 3rd gym.
Ash Greninja is in the game, but there are no new Megas.
Personally I think the inclusion of "gym" there, along with the fact we know Dexio and Sinna start the Zygarde quest, really hurts this post. And I believe that predicting a Darwin's finch/ Hawaiian Honeycreeper type Pokemon for a Hawaii island setting is not outside the realm of possibility. These are after all birds covered in any first year Biology course and make sense for an island setting.
If you put more faith in the prediction of Oricorio than I do, and believe the "gym" nonsense was misremembered, then type breeder cat is still plausible.
I do not.