Who here thinks that the non-map specific achievements should be obtainable on any map, not just the DLC pack maps? Like the old Halo 3 achievements. Or would it be better to change the description of all the achievements to read; On Castle map pack maps, …?
Ummm… When you say “non-map specific”, that actually means they CAN be done on any map. I think you meant to say map specific achievements.
But on topic, the descriptions of those kind of achievements does say “In Crimson matchmaking” or “In Castle matchmaking”, meaning the achievement can only be done on one of those maps. So no need to change it if it already says it.
The achievemets are part of the DLC so I guess its fine that they must be done on those maps.
Also I think that can be used as a bait/incentive for players to buy/play the DLC. 