I’m curious, has anyone had an experience where AA enforced this rule so strictly, ie not through-checking a bag for a 16 hour 40 minute layover? I understand they would be legally entitled to refuse it, so the OP is wise to research other options. But I’m pretty sure I’ve had my luggage through-checked on more than one occasion with a 17+ hour overnight layover in MIA.

If I were the OP I would plan to NOT ask a bunch if questions about the 16.5 hour limit at check-in, but instead just ask rather casually, “oh, and you’ll be able to tag these all the way through to XXX, correct?” But again, curious whether others have experienced strict enforcement.