Sandbagging was a major alignment concern even back when AI alignment was purely a theoretical issue.

"AI hiding its capabilities" is both a concerning sign of "that AI might be plotting something", and a great way to get blindsided by a sudden capability jump when it stops doing that for some reason.

I tried out a GLM-5.3 model and the thinking trace was full of "wait, what if I'm running in this specific benchmark? Then the expectation is foo"