Cats can jump anything ...

Your cat may have hip problems. Also, jumping on top of and then going over is the standard cat way of scaling fences/doors/etc. They do this as, you don't know what's on the other side of that fence, just clearing it like a dog could have you plummeting to your death on the other side.

Your cat, is not stupid.

They are all different...I have one that drinks by putting his paw in the bowl then licking the paw,. Cute but weird!

Yes but cats figure it out nevertheless.
My Kali, who had diabetes and caused partial paralysis in her hind area, would still figure out ways to get up on my bed...

Smart cat

lol the black spot on her chin makes it look like she's really shocked when looking up