I just did another test where I copied my entire 10,800+ song library to my phone using a fresh portable instance of MusicBee and I can confirm that reverse sync (0.5.5) appears to work as it is supposed to for ratings and playcounts
I am reasonably sure the issue is because the device cannot display all the results. I will wait for your feedback first but I have the next version ready with a change to restrict the number of results displayed.
(I briefly tried syncing playlists, but couldn't figure it out and didn't care to learn right now). I only tested a few tracks changing ratings and playcounts at a time, but the preview scan only took a couple seconds and didn't "scan" indefinitely like before.My main portable instance of MusicBee still doesn't work, so it appears that the issue I'm having has to something to do with my library file or settings
because when I transferred from an installed version to the portable version yesterday, I imported my settings and library instead of starting new like the test I just ran. The amount of files scanned doesn't appear to make a difference.
I'm going to a take a break and then try to figure out if I can import just my playcounts from my main library into my test one, and then manually rebuild everything so I make the test library my main one.