I do appreciate when docs try to protect the patient - sometimes there is a pushy or controlling relative who SHOULD be excluded but the patient does not feel strong enough to do it, and may need the doc to intervene.
Seems to me the best course of action would be for the doc to say something along the lines of "We need a few minutes to speak privately but we will call you in when we're ready for you" - that would give the doc and patient a chance to speak privately and the doc can ask the patient if they really want the other person there. if they do, it shouldn't matter WHO it is, family or not....they should be allowed in. That's my opinion.
It could also be that this was a known situation and they had a reason for being as adamant as they were - either because they knew the "helper" was problematic, or because they knew they had to discuss something unusual with the patient.
Or maybe they were just being jerks, I dunno.
It's funny, but I just saw the OTHER end of that spectrum - the last time I saw my Rheumy my husband wanted to come. I called the office a couple days ahead of time just to make sure that was okay, and to give the doc a heads-up...they front desk just laughed - the woman I spoke to said "honey, you can bring whoever you want - you can have a party in there - as long as everybody fits in the room!"....