BT6 Double Diamond does not give face to green color, it doesn't even have an SR card, no new LV7 digimon. Bandai introduced new 10 green digimon while other colors have at least 12 new digimon, this is maybe their strategy to boost up popularity for red blue and black.
By the way, Nidhoggmon is still remaining as a very formidable digimon for green color, the power of "returning all opponent's rested digimon and digimon with 5000 DP or lower to bottom of its owner deck" can deal with any type of deck. Last time we talked about how perfect the combination of Nidhoggmon and HerculesKabuterimon, now Nidhoggmon has a "even better" partner in BT6 booster set, it is AncientTroymon