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.
Not the best clip summarizing this episode, but South Park has a great take on this.
https://youtu.be/C3WsfViEwxQ?si=D3dVt0vcfiZ3vdWU