No need to open the face, according to this guy. Unless you are at St Andrews and must get out of a 20-foot-deep bunker, then yes. Or if you are a pro and want to land the shot exactly within a 2 square inch area, then yes.
But most of our sand shots in TV are not hard ; we just want to get the ball out. That's easier to do with a square club face.
https://www.youtube.com/watch?v=UKmIA5vGchQ
He's not the only one on YouTube giving the same advice. Opening the face is definitely overrated for the typical hacker. Hitting down and through the ball (not quitting on the shot) is the ticket.