I got an email and a letter from BofA about this too. If I was still focusing mostly on cash back instead of points I'd definitely keep the card's bonus category locked on online purchases.
That said, maybe I'll try doing a test purchase from Amazon at some point and see if it actually counts for the 3%. Assuming someone else doesn't do it before I get to it, of course.
BTW I doubt Apple/Google Pay in-person purchases will count. At least on Chase, those show up as in-person purchases.