Excuse me, is this thermophylae's bug? Or is it a feature?

https://www.chess.com/clubs/forum/view/thermophylae-bug-or-feature

Here is the post. As green, I made blue stalemated and captured red's ferz royal. (This was possible by having Yellow's King move)

It’s likely unintended, probably the fact that yellow is a checker and not a F-Checker, meaning that it checks randomly and doesnt care about preferences (not making a side lose, etc.)

I don’t think this is a big issue that can be exploited though, red can likely block green from doing that in the first place.

this is very unlikely to happen tho, if that did then nice

what is the problem?

add a variant called multi layer where you play 2 chess games at once and when you lose a piece in one game is get rid of the square on the other board