Am I misunderstanding an aspect of the MSS strategy?
The situation is where you are facing an EP opener with QQ and 3-bet, but get 4-bet. Here, without specific evidence, I would put the opener on QQ+, which would make QQ an easy fold.
4-betting AK would be a bluff against a 3-betting range of QQ+. Is it assumed that this (or other hands) are in the opener's 4-betting range?