My understanding is AAA is literally just a buzzword in the vein of AAAA. It doesn’t relate to budget, team size, publisher/no publisher, kind of same as indie at this point.

It maybe made a little more sense when it was a publisher descriptor? EA, Activision, Ubisoft were publishing games at a different scale than Midway, Acclaim, THQ, etc. But still, as far as I understand is more of a marketing term as opposed to designating anything specific.