Hadn't updated this - my son certainly seems to have "gotten over" it. I think perhaps he really might've just been apprehensive about those random little attractions we get sometimes and thought it meant he "had" to be bi or something. Of course, he could just have decided to hide/repress/etc.

Anyway, he told me he felt better about it and I reinforced that it didn't matter to me, that I love him the same either way. Pretty sure I managed to not look relieved, even. Thanks for all the advice and support so far.