I have this same issue, have read this entire thread and do not see any solution. I am syncing to folders with many sub folders and many large files per subfolder. But with selective sync turned on I would expect the ".rsls" place holder files to sync up quickly since the entire file is not syncing across the network. but it seems that each .rsls placeholder file takes 15-30 seconds or so to show up so it will take many hours for all the placeholder files to show up. Is there any settings that can be changed to increase the speed of the selective sync? Everything seems to be working but very slow. And it's not a bandwidth issue because I have about 180 Mbps download 10 Mbps upload speed.
Note: some files take longer than others, like a minute or two. And perhaps this is just how long it takes to sync those files over the internet and if so I am ok with that. I just want to know if there are settings that can be changed to speed up the selective sync of the placeholder ".rsls" files.