alt Hacker Newsfwiw: when I've uploaded tracks I've purchased, it almost immediately locks them because they're copyrighted... because AFAICT it's a feature for independent musicians to upload their own stuff, not a library backup. all the text around it seems to support that interpretation.
oh that's interesting. i'd tried it several years ago but had not tried uploading anything like you did, so had not noticed that deficiency (randomly).