Hey man. I suppose it's not a common occurance for people to want something that I guess usually stays idle and is used for looping tiles to boost performance.
Through personal experience, I've never really came across this sort of scenario of needing collisions laid out like that.
If I ever use a Tiled background, It's usually for something that I need looping for quite some distance. Also, say for example I made a long ground, I wouldn't have much power over it's collision polygon since it's disabled, therefor I couldn't make it so the character is walking on it as I want it to.
I do think though, that animated tiled backgrounds could be really useful for backgrounds and stuff, but maybe all this stuff (including specific hotspots)are disabled to boost performance or something.
Overall though, I just don't have the need for needing a tiled background to collide with something- I'm usually colliding things with the tiled background, or not at all lol