The definition of support is completely blurred in a game like Destiny. It is not technically feasible to have discrete tiers of endgame content based on what a particular player's last content purchase was. Besides, all of this is academic anyway, because it's talking about group content in a community that has by and large moved on to new content. Even if there was a "legacy Nightfall" option, I doubt many people would be able to find a team in the first place.