I think it’s hardcoded, just to say don’t expect an instant stop (as some people do) when button is used.
There’s been a good point made that the “Stop now” button is misleading unless you read the fine print.
Stop now doesn’t stop immediately (and I’m not sure that Issue was actually filed suggesting new text).
Wonderful find. I’m not a Duplicati dev, but this may be an excellent thing to file as Issue or pull request.
That will get it a little closer to the developer team, although the right expert might need to be brought in.
Duplicati is always looking for help (more things to do than people to do them), so thank you for helping.
If you think the lowest-level SQL statements might help, turn on profile-all-database-queries, but currently it sounds like that might be overkill. Regardless, good luck to you and @Xavron in debugging.