The beauty is that with half the amount of DEC I put in the liquidity pool I still get the same amount of airdrop points as before because every DEC in a liquidity pool counts for two points

I do not get the point: Of course you get double airdrops for pooled DEC. But you have to invest the same value into the counterpart currency of the pool (SWAP.HIVE in your scenario). You could have just taken the money you used to buy SWAP-HIVE for buying DEC. You would have ended up with twice the amount of DEC - ergo twice the amount of airdops...

In the end pooling is not more efficient in terms of airdrops. It just might have the normal advantages and risks that liqudity pools always have...