My children aren't in high school yet, so we don't have personal experience in our family, but fwiw I suspect, like all programs, a large part of how the program works depends upon how the local staff choose to implement it and their vision. I'd be concerned about the principal's statement, but would look for input from other families who's children have been through the program at the school for a good idea of what the program is really like. Our local IB (and our local high school program for HG+ kids) both have reputations of being programs where the teachers equate high achievement with high amounts of homework. My 2e ds struggles quite a bit already with the amount of time that homework takes for him - the work itself isn't a challenge (intellectually/conceptually/etc) and he's got a great system of accommodations etc.. but I'm sure he's spending much more time each night completing his homework which is a combination of 2e + his own inner drive and curiosity. When I look at what's out there for high school for him, the IB and HG+ program are the two that would seem to fit best intellectually, but I also don't want his high school experience to be all about hours upon hours of nothing but never-ending homework. So, no real advice here but a lot of empathy.
Best wishes,
polarbear