Agreed, an airdrop to liquid as well as SP does make more sense than just SP. (On a related note, I still fully support getting rid of Steem Power, but that's a topic for another day.) That would indeed make it identical to burning. "Psychological factors" play a substantial role in the crypto world, so the option which leads to better PR is the one to go for. I have no idea which one would be better psychologically, but both burns and airdrops do often lead to significant demand for the tokens that execute them.