I guess it depends on where you are.

Let’s take the scenario where there are no other cars on the road, you’re in the lane that stays open driving next to a car in the closing lane, and you arrive at the merge point. In this case, you should keep going as normal, and the other guy should fall in behind you. (Ideally he slows down to fall out of sync before getting there. Less ideally he speeds up. Least ideally you both speed up and make chaos.)

If both lanes are fully used and there’s a line in both, same situation. First car in the open lane goes, then first car in the closed lane, then second car in the open lane, etc.

Now the controversial case where a bunch of well meaning souls have lined up preemptively (causing the congestion to press back further) and some asshole just takes the closing lane all the way to the end and winds up next to another car. That car should proceed and the car behind it should wait to let the asshole in before proceeding.

It feels wrong, but it’s the least problematic flow. Effectively closing the lane prematurely pushes the congestion back further and starts disrupting other intersections