Alright, then I understand. I fully acknowledge it's not a theoretically perfect solution. That's why I don't prefer it myself when perfect solution does exist. I just want to know what you think because if I'm wrong then I want to know about it so I can correct myself.
Data should never be lost like this, but you might have an error-stall on occasion because a access happened exactly in the short handover window. (needing a resume, and possibly a re-check).
Ultimately it is much better to do it cleanly from within the torrent client, and there are plenty of good clients that support features that make that possible. It's a nice option to know about though in case you ever need to deal with similar issues in other programs that don't have any such options.
For example, many rendering programs use temporary files. You definitely don't want to upload those, and maybe they are not easy to just filter out since they could share names and extensions that you generally do not want to ignore. In that case min-age should work almost perfectly to ignore the temporary working files as the file-access there isn't nearly as unpredictable. Torrent clients really are about the worst-case possible.