Most protected lefts have sensors so they don't go through that phase if nobody is waiting for it. The sensors are another issue because they don't trigger for bikes and ebikes, but that can be improved.

I think throughput isn't really a huge issue as long as you have a few main arteries (e.g. expressways, freeways) that don't have left turns at all, you will ideally only take the local roads for a couple km at the beginning and end of a trip at most.