9 times out of 10 "at discretion" means "for extra money".
Or in my case and many indie girls cases it's not at all about extra money and all about hygiene
If a client turns up to me unclean
I'm going to ask him to shower, I'm then also going to insist on OW as no amount of soap and water can change the fact he has bad hygiene habits and lord knows what else
I'm also going to insist on OW if he has an enclosed cock and can't draw his foreskin back over the head of his cock when flaccid or erect, again no amount of soap and water will change the fact that his cock has a warm damp pocket of god knows what trapped behind that forskin and it's not going in my mouth
I'm pretty sure most WG's will tell you the same
Apart from that and the obvious sores etc there is nothing nicer than OWO 😈
(and yes I'm aware of the risks just as all of you are so no need to assassinate me for enjoying giving a blowjob)