I believe this happens because the person Sync’ing with a sound that they’ve found doesn’t realize to “Store” that sound requires they press a button on their MONTAGE... instead they repost it by mistake.
Actually the screen that appears after you SYNC, should be the one with original author’s description, audio (SoundCloud) or video example (YouTube, etc.), NOT the screen to POST Public/Private.
There is ongoing discussions about changing this... please standby. With a few tweaks it can become a very useful utility.