I am surprised by this. In general, if orientation is required and job related, it must be paid. If it's a BBQ at my house to meet your co-interns, then not.
https://www.shrm.org/resourcesandto...yworkersfortimespentinnewhireorientation.aspx
So my week of fellowship orientation, consisting of ridiculously boring lectures from the GME administrators, hospital administrators, health screening, etc. etc. was completely unpaid. I'd seen the same as you linked stated here before in a few threads, so I, out of curiosity (and also not giving a F at annoying the GME department, given that that decision wasn't made by my own division), called the DoL to inquire as to the legality.
They told me it was legal, and that since we weren't performing the work we were hired to do during that week (that is, acting as physicians), we had no recourse. By my reading of the law, that seems to be outside the spirit, but hell if I know. They also implied that the fact we could be considered interns rather than employees might be involved (which certainly seemed wrong to me).
I was a bit surprised by all that, but I didn't pursue it further. It was only a phone conversation with a random worker bee at the local DoL office, so they could easily have been wrong in their reasoning, but that's the answer I got. Plus, I know of multiple residency programs that don't pay for orientation, or only pay for part of it, and I presume at least some of them have lawyers on staff that would tell them if they could get into deep **** for it.
I suppose if they did pay for orientation they'd just divide my paycheck by 53 rather than 52 for the first year (that is, lower my pay otherwise to compensate) so it will even out... but it still pissed me off.