I don't know the terminology, but so long as the torrent is active, you're uploading. If you selectively download files, then you can only upload the chunks you have downloaded, obviously. Is that "seeding" if you aren't a "seed" with 1.00 availability? idk.
I'd still count that as "seeding" since you're running the torrent for upload only, but idk if there's a precise definition somewhere.