Yes, they're more efficient. They're also more efficient than rushing up to the end of a closing lane and merging into an ALREADY FULL through-lane. That is NOT zipper merging. It is cutting in line. That will always, ALWAYS, reduce throughput. Period.

You cannot cheat physics and human predictability. Rushing to the end of a closed lane WILL NEVER INCREASE THROUGHPUT. Period,

The vast majority of situations where people are making faces at the assholes sitting at the end of the closed lane is when traffic is already over-dense and going slow.

In those situations, which are often, racing to the end of the closing lane is just being a line-cutting shithead, and has nothing to do with zipper merging. At that point, they're literally only butting in on through-traffic.

It does NOT reduce backups. You cannot magically increase throughput by cramming in before the bottleneck. It can reduce how physically long a backup gets, which can keep backups from growing off of the highway. Though you still cannot magically add throughput by cramming in ahead of a bottleneck. Ever. Period.

OK, that's not my fault. I just obey traffic. Again, if everyone is in the open lane and you cruise by in the closing lane by yourself, I'm not letting you merge. Obey traffic.