I don't fucking know why I can't eject USB hard drives. I installed the SysInternals apps, and best they can tell me is that Dropbox is fucking with the drives. I explicitly told Dropbox to not fuck with USB drives. I don't know who's lying, I just want whoever is fucking with the drives to stop fucking with the drives, OK??? OK.
Right I get what you mean now. "File History" =/= "Previous Versions". But "Previous Versions" has been entirely replaced since Win8, so not entirely relevant.
It's also completely unrelated to file deletions, because the VSS system both System Restore and Previous Versions use worked on the block-level, and as you already pointed out blocks aren't written to when a file is deleted, it either gets copied over to the recycle bin or just marked as deleted, but neither affect the block contents (VSS works on a CoW principle, blocks are backed up only if written to, but live performance is basically unaffected by this unless you're doing huge loads like big DB modifications or something.