Possibly long enough for the person opening it to think twice about the consequences of the action they were about to take?

Same concept as putting high barriers on bridges, or selling paracetamol (acetaminophen) in smaller packs. These changes do nothing to stop someone who is committed to the act, but they provide a small energy barrier which can be enough to defeat the perturbations of a temporarily irrational mind.

I was thinking of it as a psychological tool. If the guy is obsessing about it, keeps looking over at it and thinking about how you just turn a handle and everybody's dead, duct tape could help him stop ruminating even if it wouldn't at all be effective if someone is determined.

I suspect the duct tape was there to act as an impediment and cause the person to make enough noise others would notice before anything could happen

I wonder if he had considered using the duct tape on Wang.