Yeah, it's total BS, and makes no sense.
Yep, that is the official NBME rule -- if you use soft-foam earplugs you must show them to the proctor at the beginning, and then you leave them in the exam room the whole day. This staff person insisted that you had to leave them
in your EARS the whole day, which, as you said, is a totally unreasonable request. I tried and tried to dispute it, but she wouldn't budge

And since it was a Sunday, i couldn't call the NBME candidate care center for help or anything.
In retrospect, I wish I'd just left and rescheduled, cause it totally effected my work speed and ability to get through all the questions. I've always been a slow reader as it is, and timed exams have always been a challenge, so for me, foam ear plugs are as important a tool for adequate speed as the white board is. No matter how fast I tried to race through, I had about 3 questions per block that I didn't even see at all (added up to 21-22 total!). So, yeah I'm totally, completely, bummed, especially since my practice exam scores (where I always finished all the questions, if barely!) were in the 220-225 range, which is already kinda the minimum cut-off score for Rads interviews. So since my real score has to take a big hit from all the non-answered questions, I'm thinking I better start trying to love another specialty.