Hold on. No it doesn't.
The only other clip that shows the Trainer walking around in the OW doesn't show a Pokemon following behind them.
IIRC this is past the point where you get your first Pokemon. Why isn't it shown behind the player character? The only explanation is Game Freak somehow added some sort of toggle feature for it (which would be an odd move for them but w/e).
I would love Pokemon following you to return, but I'm not getting my hopes up until it is
actually confirmed and I see consistent footage of the such, not just one clip.