It is a bug, I’ve seen it hundreds if not thousands of times.
You won’t see yourself doing it, ever.
It’s a visual bug, it only happens if viewed by other players.
I had a friend see me go sideways while I saw him going sideways, however on our own screens we were both moving normally.
So yeah, he’s probably a bot dude.
Or something.
That’s why I have opened it for discussion I have never seen this before.
Ghost wolf form, moving backwards at full speed too just looked utterly bizarre.
Like Valkia writes, it’s a bug. Sometimes it happens to people i’m in group with, they can’t see it themselves. You could be running sideways and backwards on your epic mount yourself and have no idea.
It’s been that way since TBCC launch - i dont remember seeing it in classic era.
This is a feature of Classic. A visual bug that was part of the game for a long time. It was much easier to recreate in Vanilla/TBC retail with the old client than in Classic with the modern client but it still do happen.
But when you talk about “full speed”, I have doubts that you actually saw what you think you saw. Speedhacking do happen but it sounds like you just beleive it was at higher speed than it was. If it was a lvl 60 shaman they can run at almost mounts speed with pvp boots. Maybe he was on his mount and there was a visal bug. Who knows.