It all comes down to this for me: There should never be an excuse to not perform OWO.
I think a sp can and maybe even more controversial under some circumstances “should” refuse owo.
The reason I say this as follows. If punter turns up having not showered, smelly, dirty, and unkempt especially down below etc and they refuse to take a shower when offered then the sp can refuse the owo. The punter may be paying for her services but as punters we should also maintain a certain standard.
As for when they should I think plays more in part to potential STI transmissions and protecting herself and other punters who will visit after. I personally see WG’s that offer owo and it’s very much a deal breaker. So I would want to be confident in that the wg I see isn’t harbouring any nasties from a previous punt. And as a sp imagine a punter turns up with nasty rashes, spots, boils, etc and then expects owo. In my view that would be unacceptable.
I know that you and the majority of us punters who enjoy owo do keep ourselves clean, tidy, and in good health down there so it’s not much we have to worry about when punting. If I get refused I know it’s Bullshit but what I am basically saying is under some exceptional Circumstances a SP can/should refuse OWO