In theory the Borg have assimilated the biological and technological "distinctiveness" of humanity and the Federation through proportional representative sampling.
Cataloguing why we are awesome, and adding it to the collective is already in the bag.
The 400 billion new Drones should have been just gravy and unnecessary.
If they're coming back to Earthspace to update their understanding of the Federation, that's kosher, but if its just because they think they've been short changed in their Drone recruitment, well fuck them. Altruism, cheap sons of bitches, my submersible ass.