Ohhhh, is that why it was spinning going into the reentry attempt?
Now we just need the Attenborough voiceover about the mating habits of starships as they spin through space.
That would send fluids to the back of the tanks.
At this stage it might be easier to build fueling station in the orbit with actual transfer pumps.
As for spinning two Starships of significantly different mass... that should be interesting to see. Doable, yes :) but interesting nevertheless.
Pushing the liquids is not the hard part. Settling the liquids in 0g is the hard part.