A lot of scenes seem to be shot in real hotel rooms (not filming sets) though. I wonder if they just book a regular room and then a group of crew go up with with cameras and lights in luggage, then the JAV actor and girl to up and they are shooting all day (usually looks like daytime when they start and then end at night by the light in the windows).
I'm thinking of some of the series from S1 or Ideapocket where it looks pretty clearly like a upper end hotel. You can see out of the windows that it's a high rise in a business district and the furnishings with multiple beds, clocks on the nightstand, sofa, sizeable bathroom, etc. are typical of nice hotels.
I don't have the link handy, but there's websites that have lists of non-love hotel hotels that are "OK" for calling in escorts (ie, front desk far away from elevators).
I'm sure studios will reference these when wanting to shoot in one.