Because with AuxPoW, a Doge is tapped into all scrypt hash power.
ALL?
Incorrect.
Doge is tapped into (sharing) Litecoin's hash network. Just like all the sha256 merged coins are sharing the network with Bitcoin.
I believe the AuxPoW fork code allows the sharing of any script coin with a hashrate higher than that of Doge, which at this time is only LTC.