So several people replied with this same thing, which I have heard before being suggested. However, as I recall it at the time, if you tried to search for "invert binary tree" this term basically did not exist on the internet. I just tried searching on google with time set between 2000 and end of 2014 which seems to give similar results.

I guess I did not spell it out in my original post, but I always felt it might have been an intentional nonsense question intended to gauge how he would react to someone talking nonsense, or something like that, and not necessarily related to technical things. A sibling post of my original to suggest this was the case, without the weird detour through the term "invert binary tree".

Edit: Of course an alternative explanation is that the interview used another term and he then used the term "invert" on twitter.

Idk, this example at least has to me always felt like people who complain about not passing the driver's test coz they did some minor error and then forgetting to mention that they drove past a stop sign.