Well it does work both ways.
If she's legit or even if not, she may quite happily devote that time to other clients who happily accept whatever conditions she would like them to comply with.
And have received plenty of great massages even if one must be partly covered.
One of my very 1st massages was partly covered at a 100% strictly legit, strictly policed, massage shop, and absolutely no chance of anything untoward happening ever, ever, ever.
Toward the end, the very nice lady - "I should really do something about THAT for you before you leave".
Um yes, that was a surprise.