These are ultrasound technician students, the ones who do the actual exams. Physicians don’t do the exams, and wouldn’t know what end of the power cord to insert into an orifice. (They would know which orifice, however. I hope.) All they do is read the report.
In general the best way to learn is to do things, after you’ve learned the theory of how to do it. Students in medical fields often do tests on each other. But in this case, it should definitely be optional. Say someone had fibroids? That probe could really hurt. And I wonder: did they actually turn the ultrasound on? Seems to me that violates the ALARA (as low as reasonabley achieveable) principle; in other words, don’t subject the body to invasive energy input unless there’s a definite need to. But I don’t know how ultrasound training implements that, if at all. Maybe they’re irradiating their own hearts and brains for practice, instead of being mentored at bedside on patients who need the tests.
It’s telling that the school claimed it was “voluntary” when clearly it was not. Four Pinocchios.