They're so obviously real. Anyone who screams fake just because they dislike the designs doesn't understand how Pokemon evolution, especially the starters, are designed.
If you look at any fan art of what people speculated the final evolutions of any of the starters would look like, the fan artists always just draw a bigger, cooler looking version of the original form. Gamefreak there are exceptions, of course, but i'm talking about the majority don't like this, and instead usually try to incorporate a flowing theme between the three forms rather than make them look similar.
If you look at these fan art images of final evolutions for the Gen 6 starters, even when the artist had the information of what the second forms looked like, they still did exactly what I said they always do. They're just bigger versions of the last form with more detail. (I do actually really like how the "Greninja" equivalent here looks and wouldn't have been upset with it)
Instead of what we had here, GF decided to run with, for example with the Froakie line, the pokemon becoming more and more ninja like, instead of making it a bigger more powerful frog. For whatever reason, they decided to get rid of the keromousse around the neck and replace it with a tongue, probably because it looked cooler and let them add in another thing to really express the fact that it's a frog. To compensate for this, they added the white that was there before to the side of Greninja's face.
Now if you look at Popplios final evolution, the little "ribbon", for lack of better words, around Popplios neck has become incorporated into the full design to imitate a dress. The white on Popplio's nose has taken over most of its body, with the blue moving down to its lower half. This recurring theme of just taking features from the older evolutions in the line and not just making them bigger is true for each of the other starter final evo's in the leaks too. I could seriously write an essay on this.
