I’ve flown on AA’s international business and first class. The difference is negligible in terms of the seats and most people in them were complimentary upgrades since they couldn’t fill the seats.
The bigger differences were on the ground with the dining and check in. So all AA is doing is creating a “Business Plus” category that gets you the first class amenities on the ground and then a business class seat. This lets them put more business class seats on the plane and open things up to a bigger revenue stream.