Not sure the actual amount, but as far as I know, there are two cards, Alishar and Manon, that don't move while they should be animated. Here are the pics.
I think that certain mobs had their animation disabled because the animation is too big. Alishar can flip midair, which would go outside of the book's space. Manon has the fire breath. there are more big bosses that had their animations disabled
Very interesting point. But there are mobs with similar size or skillset with animation. Could possibly just a bug without special reasons. After all, I didn't collect every card, so it's hard to tell.
This is correct for a lot of the bosses which don't have an animation showing, and there are also bosses like Zakum and Horntail which have a non-animated image due to them being built of multiple mob images. The consistency of some images being static and some being animated for big monsters is definitely questionable, I would think that it makes the most sense for any bosses which have an animation that extends out of the monster book page to have static images instead.