I was going to post this in a separate thread, but when I saw your link in my thread, I thought it might be more appropriate here.
I was just reading in some literature supplied with a battery charger that the correct finish voltage for a 12V flooded battery is 14.84, while the correct finish voltage for a 12V gel or AGM battery is 14.4.
This may cast some dispersion on the use of AGM batteries in our old British machines, and may explain why my Scorpion AGM battery only lasted one year. (I was withholding this conclusion because, during that year, I had a faulty alternator lead for a couple of weeks. However, I noticed the charging problem right away, and prevented the battery from going completely flat through external charging.)
After that, I bought a flooded battery quite by coincidence - I needed a battery in a hurry and the only one I could find locally was a flooded battery. However, this battery has performed flawlessly over the last two years. Notwithstanding the dreaded acid leak potential, and having finally figured out how to make the dang hose stay on the breather spigot, I may just stick with flooded batteries (or "sealed lead acid", which has the same charging requirements as a regular lead acid battery, but without the potential for acid seepage).
But this is with an "OE zener diode". It would be interesting to see if the specs differ with a modern rectifier/regulator unit. I believe many modern bikes call for AGM batteries, so I have to believe they've taken this into account in their charging systems.