Hi Mike,
Exactly same situation as you, the only work around is to use the Vault, it's annoying because you have to wait for it to download the files everytime you access it and then if you forget and keep those files open longer than the allocated time of 20 minutes it has a meltdown and takes some time to correct itself. It's a shame they can't make the Android system function the same as it does on a Windows PC.
Yes agree people could 'with selective sync, if people know where to look, they can easily re-enable those folders to sync again' but in mine and probably Mike's situation this would be unlikely.
Kind regards
Rob