They might have updated the package before they made the decision to drop J1? Maybe they were going to update it to just one 4.x release then drop it?
Or might be for people who like pain and format MicroSD cards as BTRFS?

Coincidentally my J1 hosed itself trying to upgrade to the final release by strangling itself with its own BTRFS metadata (a constant problem back when I was using it regularly) while updating. Booted with lots of dependency mismatches and no UI, now won't boot at all. I tried to resurrect it, and still perhaps could, but frankly I can't be bothered. It died the way it lived, with a self-immolatory filesystem.