I often leave a download for a second, then set all files to do not download and let it seed the chunks it has. Which works with the latest version. But when a torrent has a single file it's not possible to mark it as do not download.

File deselection is only implemented for multi file torrents, because the reasoning was you might not be interested in all files. This obviously doesn't apply to single file torrents, because if you are not interested in that single fileyou do not download a torrent

And then somebody came along which wanted to deselect a file and keep the data around to continue seeding it, so we added this only seed priority for files. Until this change, deselecting a single file torrent didn't make much sense.

I guess we could add this, But don't ask me when.

no rush really , I very rarly seed chunks on single file torrents. But I thought I'd mention it anyway