Chaos:
I'd prefer the bug were fixed and this wouldn't be an issue.
I don't intend to have games against players that aren't skilled enough to know a move is illegal or that a particular position could lead to such a move.
A player can look at the previous move prior to beginning the move and look at the move list during the move to verify that all pieces are moving according to the rules.
Anyone who doesn't want to risk making the agreement certainly doesn't have to.
Nevertheless, I don't mind adding to the description:
It will be at the players discretion against whom the illegal move was made to either ask the opponent to resign or allow the opponent the opportunity to have the illegal move reversed.