[quietbritishjim]

I can think of things where I would leave out details that a non-expert would need filled in. Except, I wouldn't do that in an interview situation where someone is specifically asking me to explain that one thing. (Yes they started with the giant coin thing, but "symmetry" is still the substantial majority of their argument.)

The sibling to my first comment says it a lot better than I did: in a similar but different situation there's symmetry but no analogous strategy, so further explanation really is needed here.

In a sense, that makes it even more damning. Eliding details that you don't realise are important, but actually are, shows a real lack of understanding of your own argument. And that's something I have definitely witnessed in my own field!

[Y_Y]

Oh man, I assumed he explained it in the interview and was just leaving out the details for the purposes of the comment. That was me being dense.