I don't know what the AGM batteries will accommodate, but that is high for an alternator. I thought most auto alternators run 14.0-14.2 range. In a flooded battery, in the upper 14's you are in the equalize stage and your losing electrolyte. Put a meter on your battery and test. The only thing that matters to the battery is the voltage on it's terminals
Just a data point - I thought 14.5 would be high too, but I took an alternator off a late model Tahoe and it tested at AZone at 14.5, just like on the vehicle. Their chart said 14.5 was the spec, and the new one from the box tested exactly the same. I reinstalled the old one.