I guessed that, but still can’t figure out what makes ℂℍℙℚ special. Looking again, I notice ℕ is taller, too, but not bolder. ℂℍℕℙℚℝℤ is much more “I can see why a font would have these, but not others”. That solves the issue enough for me.

(And, by the way, iOS doesn’t have Geneva, but it has a version of Verdana)