I guess it depends on what situation we are talking about. Is it already f’d and a bottleneck or are we being proactive to prevent a bottleneck. If it’s already a bottleneck the. You’re correct. If it’s not a bottleneck then I’m correct.
But in those instances when traffic is free-flowing through a lane drop (like in the photo below), then the early merge is the best thing to do. Merging early in this situation is safer and helps to maintain the free-flow of traffic because, as mentioned before, drivers who wait until the very last minute often need to slow considerably or even come to a stop in order to merge, or will sometimes just shove themselves into the through lane. Someone in the through lane then has to slow considerably or even stop to allow them to merge, which then causes the person behind them to slow or stop, and the dominoes fall from there and becomes the genesis of a traffic jam or, worse, a rear-end collision. Merging well in advance in that situation allows drivers to find and enter a gap when other drivers only need to make minor adjustments to their spacing while maintaining speed, thus preserving the traffic flow.