The Moorish Idol also has special significance for some religions, and I wouldn't want to offend anyone.
Ah! The real reason comes out. If that's why, then I guess I can understand.
I hold firmly that the Moorish Idol and Wimplefish are farther apart in appearance than the Wimplefish and the Three-stripe Damsel.
As for the Batfish, the fin height can't be any harder than the Lionfish spine width can it? Granted you can't have the Batfish fold down its fin the way the Lionfish folds in its spines to get around a corner. (Watch for it, Jim added this in the current build of 1.1!)