I think this may be more just trying to block out how stupid the new rule is and how it makes the AMS of very limited use.
Actually, it does not.
With the old rules, AMS would destroy about 12 (24 for Clan AMS) missiles, then become useless for lack of ammo, unless you gave it more than one ton of ammo. IIRC it would also waste itself against missed missile salvoes. Basically it was good for three or four rounds per ton of ammo.
With the new rules, sure, the number of missiles destroyed each time it activates goes down, unless you have IS AMS and it intercepts salvoes of 20 or more missiles, in which case the number can go up considerably, up to (IIRC) 16 out of 40. But since its ammunition lasts so much longer than previously, over the course of any battle that lasts more than about four rounds, the total number of missiles destroyed will be considerably higher than under the old rules.
If I had to choose between old rules and new rules, I´d prefer the new rules. Though if I could pick and choose, the old rules´ effects and new rules´ ammo useage would be an even better combination.