That's not the point. The point is that if someone can't do some of the easier Leetcode style problems, they probably didn't try to prepare at all, and that can be viewed as arrogant or lazy.
I'm not disputing that binary trees might not be the most practical topic (especially inverting them).
However, given that one knows that is the sort of coding interview Google conducts, one should reasonably be expected to practice that sort of interview. Inverting a binary tree isn't hard; it doesn't take much practice with binary trees to realize how to do that. So if someone can't do that, they probably didn't practice at all. And if someone didn't practice at all, an employer is acting within reason if they draw some negative inferences from that.
I'm not disputing that binary trees might not be the most practical topic (especially inverting them).
However, given that one knows that is the sort of coding interview Google conducts, one should reasonably be expected to practice that sort of interview. Inverting a binary tree isn't hard; it doesn't take much practice with binary trees to realize how to do that. So if someone can't do that, they probably didn't practice at all. And if someone didn't practice at all, an employer is acting within reason if they draw some negative inferences from that.