You are correct that for example Ccminer has dmd-gr in addition to the groestl algorithm.

What makes me a bit confused is that WhatToMine, Coinwarz and the FAQ of the Diamond coin states that it's simply Groestl. If WhatToMine would have reported this as another algorithm, Awesome Miner could for sure map this to another command line parameter. Now it's getting a bit difficult, because if the above is true, Groestl could require different parameters depending on coin, which would be totally confusing.

Is there anyone else that has a good answer on this?