Not sure when or why this started...

[Nightraven]

But basically some techs are able to damage monsters from outside of the room they're cast in.

So far, I've only confirmed this with Gifoie but I expect Razonde and Rabarta to also be capable. In certain situations this enables the player to destroy the enemy without ever entering the room (except to spawn enemies).

This is relatively recent, too. So I have no idea if this came in with the latest DMC code changes or not.

 

[Spuz]

This has always been possible (afaik).

 

[CTB]

Yeah, it's something that has been around since forever. Has its uses but is generally not useful enough to be a "problem" exploit.