In the achievement description it says In Crimson DLC Matchmaking, board an enemy Mantis etc. So it seems the achievements are map locked, might even be playlist locked, anyone confim this?
im sure you have to be at least on a crimson map. maybe not the playlist but at least the map. and once you get to playing the maps youll realize that only certain achievements can be gotten on certain maps just because of how they are set up. one has two mantis and two mounted turrets. another has man cannons and the third has big hills and warthogs.