Yes, although I've found alot of theatre toilets & the like don't cope well when used non stop and block easily, or are slow to refil so won't flush if you've gone just after the last person. As a general principal I think always flushing public toilets is more hygeinic. If she really thought it was OK she wouldn't have commented on it. I doubt she comments that she's flushed because she's had a poo!
What I want to know is: who is the kind of person that smears shit on the toilet seats and walls of cubicles?
I have encountered this a few times now - in fact I was at Somerset House this weekend and went to use the toilets there and one of the toilets had shit smeared on the inderside of the toilet lid. HOW does that even happen? HOW does no one ever get caught doing it?
I'd say she probably couldn't flush it (they can be bloody slow to fill in theatres/bars etc)& she was just warning you.
I used to work in a busy club & the toilets never filled fast enough to flush properly - feeling quite faint at the memory now but OMG the chaos it caused (thankfully not my job to deal with it but still I was witness to some regular horrors.