I think it actually should work better than the usual method. With the old use case, you'll be uploading for the duration of the download, and once it's done, you might stop seeding and start watching your movie or show. But while streaming, you aren't likely to bother to stop seeding while watching, especially if the app doesn't go out of the way to interrupt your show to tell you it's done downloading. So while your average user may be uploading bits in the worst possible order required to keep the file alive, they will likely be uploading them for much longer.
It should keep seeding until the app is closed (so on average potentially a lot longer than the duration of the movie). They could also make it so the app minimizes to the tray, which could lead to even longer average seeding time (some people just close an app because they don't use it right then).
