The guidebook images do show the same 3rd stages of Grookey and Sobble as pictured elsewhere, even from a slightly different angle - so far, they seem quite convincing.
According to the guidebook pictures, all starter final evolutiones are single-type, which is nice, we haven't had that in 20 years (though I would have loved a Rock-type star Grookey).
As being animated has become an integral part of Pokémon design, the still images we have certainly don't show us the whole idea behind them or how cool they actually are.
Imagine having a still of Decidueye without it shooting arrows. That's what we've got.
The Grookey final evolution, supposedly called Rillaboom, looks great. It probably has a neat way of putting its drum away when not battling that we are yet to see, like its pre-evolutions keep their drumsticks in their hair (can be seen in leaked images of a camp).
The Scorbunny final evolution, supposedly called Cinderace, is too blurry in the guidebook image to make out anything more than that it looks like a footballer in a jersey. I need better images for opinions.
The Sobble final evolution, called Intelleon (I refer to the old leak that predicted everything correctly for that one, its name isn't in frame in the image), looks the most unusual to me. I do like it, but I can't see what it is supposed to do, or why the head fin is shaped the way it is... This is a problem of the unmoving image. I eagerly await seeing it move to clarify this, and then it will surely be an awesome Pokémon James Bond. I do see a tuxedo. It might have all sorts of cool spy gadgets incorporated in its body that we don't see (Decidueye situation).