That's kind of the entire issue - I'd hope for a full bleach scrub after that, but hosing it off outside would just be so much quicker than a deep clean of the shower, so I feel like there's some conflicting incentives here which suggest a deep clean is not certain.

But more to the point, psychological cleanliness is not always entirely rational. For me the shower is kind of a sacred clean area, so any attitude which includes using it as a utility sink for feces-adjacent activities conflicts with that on the surface. By the time I'm thinking "how well do they clean it afterwards?" That core psychological safety has already been compromised to some degree. Likewise, a shower with soap scum and discolored tile and dingy fixtures would make most people feel "less clean" even though there is not rational health issues from some simple deferred maintenance. Most people feel "cleaner" when the shower itself appears clean. Knowledge that the shower is not used as a utility sink is exactly the same.

I mean I can't imagine getting bits of kitty litter down your drains a good idea.

Yeah, I have no idea what the best procedure would be, but I think the only things to worry about are foot fungus (no idea if there's any risk, but your feet are very much touching the shower floor) and rinsing the soap if you drop it when showering? Like, you wash your ass in that shower, it's not like it's a clean clean environment anyways.