Ok, some more info found..
This bit doesn't seem to be used under one scenario.
The conditions:
1) The monster has the boss bit.
2) The monster spell is reflectable.
Those are the only instances where the boss bit is seemingly ignored, though, it could be some other check I'm not aware of.
Count/Doom, Magnet (Stop), and Disrupt/Dimension 9 (Death) (and possibly more) seem to ignore this check... hmm, I wonder...
If someone could look into it, that would be appreciated. This could be specific to a number of things...
1) The spell code (probably) - it seems to be monster spell code specific...
2) The monster itself (somewhat likely) - it just has bits and a battle script.. which makes it doubtful.. although the Trap Door isn't resistant to Death status normally... and neither are those status be resisted naturally...
3) Reflect status (probably) - it does a lot of funky things
4) The monster is the caster (somewhat unlikely) - see Dark Elf fail to get hurt by his multitargeted Tornado when someone has Reflect... although it manipulates HP.. so that's possible
It's also curious to why Laser (Dr. Lugae's attack) fails to hurt himself.. but that could be due to it dealing damage...