Unless a player's cleat is green, this is a very simple, black and white call.

If there's no green between the players cleat and the sideline, the cleat is touching the sideline and the player is out of bounds.

I have no idea if the picture you posted is an angle the replay booth had for review. I also don't know what angles they did have access to for review.

I will say that the picture you posted above looks like the official on the field blew the call.

The picture is at a slight angle so it is possible that there may be a blade of green grass in between his cleat and the sideline. However, the picture is a good closeup, which makes it highly unlikely his foot was inbounds.