I can see it maybe as a match play ploy. Make you opponent feel de-valued, and of little consequence. Get under his skin. However, I take my golf as a social thing...
Phil, did the guy talk much? Did he have anything of interest to say? Did he socialize at all after the round? Did he spring for margaritas for the group?
Just did an Aimpoint lesson with my instructor, I really like it so far and my reads were pretty accurate when I was practicing compared to what his digital level said.
Need to continue to spend time practicing to get calibrate, but I am encouraged by the results so far.
If your group is not out of position, then I agree it seems rude.
The only time I will start walking to the next tee is when we are obviously falling behind. And usually then I will acknowledge by saying something like, "hey I'm gonna go tee off so we can keep up the pace."
Whenever possible, I will wait for everyone to putt out. In a casual round, it's just a courtesy. And in a competition, it's a necessity if you are attesting to their score.
Yeah, in this case, there is really no justification for this behavior.