It is only reasonable almost all, if not, all programs will make such concessions as I believe the majority of applicants have pending third-year rotations because of our global and national (especially here in the US after the protests/riots) situation.
Yeah this is one of my worries. I am finishing up a 3rd year rotation in September and they will have 3 weeks to get my grades/comments in..... Even though it is P/F LOL
I would say no unless it's medicine or surgery (or if it's related to what you're applying into, obviously).
When I was in med school there were always some poor MD/PhDs or people who had taken a year off who were about to graduate and had to do OB/Gyn or family medicine in April with students 2 years behind them.