If some guy turns up with bad breath then she ain't gonna dfk despite maybe doing it with most other punters.
I think its naive to automatically jump to that side of the bandwagon. My experience is girls just see you as a softie and take the piss.
I doubt any girl wants to OWO anyone, or DFK any of the guys she sees but it seems to be a certain type of guy she doesn't and that is ones she knows she can get away with refusing it.
In answer to the OPs hypothetical question, there may be others, but at this moment in time I cannot think of anything that annoys/angers/upsets me more about this hobby than this.
It does affect me when I go to a booking and the girl gives out a load of excuses or states things are not done and then you read reviews saying did OWO/CIM/DFK with this girl. Or even worse still you have read the reviews in advance saying she does it and you are feeling awkward in a room trying to subtly pry out of her why she doesn't want to do this which is always a response of "I don't do this with anyone" when you know its a barefaced lie so you try to ask what is wrong with me causing her to not want to do it.
And to further expand on the 'its the punters fault'. I shower just before I leave, and many times when I get in the room I jump in the shower again for a good 5 mins and stuff like OWO is still off the cards.
And the breath I brush my teeth before I leave, and have menthol chewing gum all the way there and still DFK is off.
It is not due to cleanliness. It is most likely either a case of coming across as a softtouch, or just the girl finding me ugly as hell and not wanting to do this. No other innocent punter caused reasons which always get thrown out as reason number one.