I can’t claim to be a battery expert but from what I’ve gleaned over the years, none of thst sounds right to me.
AGM and gel batteries are not the same thing.
AGM batteries should be lighter if anything, as their inherently higher CCA ratings should allow a smaller battery to be used.
First I’ve heard that 7 to 12 amps are necessary to charge a battery. So all the charger manufacturers are supplying chargers that won’t charge a battery?
I really don’t think so…
What I’m saying applies to conventional cars of course, I know stop/start cars are different as they have black boxes that control the way they charge and that muddies the waters rather.