Cats poop in the litterbox because they want it contained. Poop smells bad. The toilet is actually better at this than the litterbox, and some cats figure that out. Especially if they figure out that people poop in the toilet. They're not all that stupid.
Cats are amazing creatures, when you think you fully understand them and their capabilities, they do something you never thought possible. My Alex, apparently can jump nearly any height from nearly any distance. We call it defying Gravity.