Once again, an AGM would have to be on a constant charger for weeks before it would be damaged by an alternator.
No one drives long enough to have any effect on an AGM, and as soon as you turn the motor off, the battery begins to settle.
This means the charging process will start all over again when you start the motor.
But the problem for your misguided theory is that, as Noki has also posted, the voltage provided by an alternator operate constantly at or above the gassing threshold of 14.7v.
But then again, with literally millions of people, world wide, charging and maintaining their AGMs in all sorts of vehicles and not having problems, where is your proof they will have a problem?
One more point, that confirms your theoretical problem does not exist is the fact that all lead acid batteries self govern the amount of current they will draw once they reach 80% SoC, and again as an alternator does not charge at a constant voltage of 14.7v or more, the batteries themselves will govern the amount of current they will draw once they are fully charged.
So once again, your claims do not match what happens in the real world.
If they did, you would have posted up a link to them.

