I believe the last form of the water starter is a narwhal... a narwhal which doesn't closely resemble it's first two forms.
Obviously, the water and grass 2nd forms must be real because those are the same from the art leaked on serebii.net in the anime. I'm assuming this could mean Pokabu's second from is real as well.
But the third forms, now that I've read this topic, you could all be right. The only one I wish would not change is the grass starter. He looks cool.
But, for the water starter, the second evolution (the narwhal) does not resemble its first two forms in its artistic aesthetics.
The last fire form looks basically like the second form (nothing much added) and side by side the last form is actually smaller (an unusual way to portray it as usually when the evos of the same pokemon are side by side the later forms are bigger). I mean, just look at them; this makes no sense:
The last evolution is not only smaller than the first and much more unclear, it is on a different layer. Look at it! The first evolution looks closer and the second looks inserted in the background. Therefore (while connecting with the legit second forms we already know from a previous leakage), I claim that the second evolutions are photoshopped fakes while the first evolutions are the real deal.
So, I think the third forms of the starters could very well be fakes, but the second forms look legit (and I'm not too proud of the fire and water second forms either).
I am also upset about the ape trio. The grass ape was already too much, and now we have a blue ape and a fire ape which could certainly degrade Chimcar in the end. Too many apes!