People sometimes use "Aumann's agreement theorem" to mean "the idea that you should update on other people's opinions", and I agree this is inaccurate and it's not what I meant to say, but surely the theorem is a salient example that implicitly involves such updating.

The theorem doesn't involve any updating, so it's not a salient example in discussion of updating, much less proxy for that.

Should I have said Geanakoplos and Polemarchakis?

To answer literally, simply not mentioning the theorem would've done the trick, since there didn't seem to be a need for elaboration.