Somewhere, somehow the AGM's differ in the way they recharge optimally.
I've read that a vehicle's charging system needs to tailored to them. The same goes for battery chargers.
I don't know if it's a huge difference or not.
I have nothing AGAINST AGM batteries.
I do believe the industry wants to say good-bye to old technology. If FLA batteries make up 99% of the business, it'll take time.