Diabetes is considered a continuum, not a series of isolated events. Considering that all knowledge is to a degree imperfect, the A1C has been accepted as the best way to grasp the state of the continuum
The average always downplays the extreme. Statistically, an average without contextual “swing” information is nearly meaningless.
I do not yet see exceptional merit in the reasoning behind this change. I do see powerful monetary reasons to suspect the decision.
BTW, to say that the A1C “has been accepted” when the change has just been proposed is premature, IMO.