It's a storage thing. You can make it so that the parts fit together better in pieces, then you assemble the pieces in theatre during deployment, so you have more drones in combat per mothership.
It's not like taking crude, cracking it, then refining the plastics, yadda yadda yadda. It's more an fast automated assembly thing.
As an example loitering munition with foldable wings is already fairly compact. 2x storage space savings might not justify assembly space and effort
Inside of a submersible warship really is not the place to be conducting assembly of sensitive electronics, and just because you call it "fast automated" doesn't mean it's either of those enough to be feasible in combat situations.