When the OEM, AGM battery failed I found someone to jump start the vehicle directly on the battery. I drove the Prius home (about 50 miles) and the smell of H2SO4 was very strong. I have used many AGM batteries in vehicles that weren't designed for an AGM battery and several failed within a few years. I wonder if the slightly different charging profiles affect battery life.
AGM normally needs 14.7V instead of 14.4V. If you never charge it with the correct voltage the battery will lose capacity.
No sorry but it won't "Lose capacity". Unless you define that to mean that it only charges up to maybe 97% of capacity instead of 100. A slower charging rate tends to extend life, not diminish it.
slow charging seems work better on AGM battery. Slow charge about 1amp on my old AGM battery for overnight and last 5-7days.