To counter your anecdote, I've also received ketamine sedation for procedures, and never have I experienced any sort of "tripping"-like effects. It certainly can be used without those effects, at least in some portion of the population.

It's a dosage thing. I was given a relatively high dose, apparently.

There are similarities in the general quality of the mental state. The BIG difference is that ketamine is dissociative. Perceptions on LSD and shrooms are still strongly correlated with real sensory input. You're hyperconscious of your real surroundings. Ketamine is more like a lucid dream where you're having a rich, strange experience, but not very conscious of your real surroundings.

Yes, that's very much how I'd describe it.