Yeah, this should happen in the core if the screen type is set to LCD, and there should be some way for drivers to "opt out" as well. Sega handhelds were notoriously smeary (playing Sonic 2 on a Nomad is a real experience for that reason), but others aren't so we don't want to pin drivers that don't have the effect with it.
Yep, and that way all the systems that need it benefit from it.
It's a common technique used on handhelds to overcome sprite limits and create transparent effects, so having it in the core means that any system that needs it can use it, having it in the drivers helps nothing in the longrun.
Is there any need for all the drama just because I disagree with something ?!