Bios update 3.09 mentions completely disabling 15V charging in thr changelog, see BIOS 3.09 Beta release
Yeah, that saddened me a little bit. After all the hassle of installing the new mosfet I might have to switch to a custom EC image to reenable it now.
optionally enabled for boards that have the right transistor
I doubt there’s a non-hacky way to easily detect what transistor a board has.