I was at Google when that happened, and had some inside sources (ie gossip from the guys who interviewed him, who said they didn't even ask any tree questions, and memegen).

I tried to find some outside sources, but nothing about Howell admitting his 'artistic license' outright. So take my fallible memory with a large pinch of salt.

See https://news.ycombinator.com/item?id=15713801 for some discussion, and to see how 'invert a binary tree' wasn't even an established term that anyone at Google would have used.