Yeah, that's poor wording on their part. It would be better to say something along the lines of, "Let me know if I get too aggressive - sometimes I really get into these whiteboard problems and I appreciate your feedback."
In this particular anecdote it didn't appear to be aggressiveness that the interviewer could control so much as a social cue/interaction issue of some sort (possibly autism-spectrum) presenting as brusqueness/disinterestedness. (Of course, that's giving said anecdotal interviewer the benefit of the doubt, because it certainly came across, at its worst, as general rudeness and an impression that even performing an interview at all was a waste of that person's time and effort. If that were the case it was even more a question of whether it was a good idea that said interviewer should be involved in interview loops.)
I realize in software we have to deal with plenty of people on the autism spectrum and/or with various sorts of social skill deficiencies, but technical question whiteboarding has enough difficulty that you probably don't also want to throw in such a difficult social interaction test in the same interview. (Not to mention that some of these social interaction/spectrum issues can lead to pedantry in a technical interview that maybe biases the technical interview in a poor way.)
I realize in software we have to deal with plenty of people on the autism spectrum and/or with various sorts of social skill deficiencies, but technical question whiteboarding has enough difficulty that you probably don't also want to throw in such a difficult social interaction test in the same interview. (Not to mention that some of these social interaction/spectrum issues can lead to pedantry in a technical interview that maybe biases the technical interview in a poor way.)