I am not a therapist but I would think you would have to go out of your way to brush up against a client with your cock or balls. I would think if you are doing a strictly therapeutic session your midsection wouldn’t get that close to the table. Once again i have only been a client and never performed a massage.
I only go to licensed therapists that advertise legit massage. In most all cases after a session or 2 there is some brushing against my hand or arms. I try and position my arm and hands towards the edge of the table for easy access just in case. Usually during the first couple of sessions there has been no brushing up against me which is why I think they have to go out of there way to do it. I almost every case after a few sessions you can feel them get a little more comfortable. I have had some guys just brush their cock , usually through there shorts or pants, against my arm or back of my hand. Sometimes I can’t tell, because I am on my stomach, if it is their cock or just their leg. But as the session goes on they will get semi hard or in a couple of cases a full hard on so there is no guess work needed. Lol. Most of the time it doesn’t lead to anything additional and when I turn over on my back the session just continued as normal. I think some guys , and who doesn’t, enjoy the feeling of rubbing your hard or semi hard cock against a guy without the pressure of it turning into anything more.
Most of the guys have provided a HE at some point but that also takes a session or two to build a trust and comfort level. If discovered or performed on the wrong person can lead to them losing their license or worse.
Just my experience of course.