I've had snack baskets miscatered on BWI<>CLT a few times too (~360-ish miles), probably more than on any other route I've flown. 500 miles has been the spec for a little under 3 years though.
Per
https://www.aa.com/i18n/travel-info/...ium-dining.jsp
Includes the continental United States, Alaska and Puerto Rico; Canada; Los Angeles (LAX) and Phoenix (PHX) to / from Hawaii; Mexico; the Caribbean; Central America; Colombia; Ecuador; and Manaus, Brazil (MAO).*
- Snack basket on flights 500-899 miles during meal times
- Meal service on flights over 900 miles during meal times
- Snacks on all flights without snack baskets or meals