The seemingly unattainable supports between... (Spoilers)

[Pie Burritos]

I noticed that Edelgard, Dimitri, and Claude all have support conversations with each other. If you go to the title screen and navigate to the support conversation viewer, you can view their support conversations as long as you've completed the Byleth recruited ending. They're the conversations they have with each other while the three are stuck in Zahras. However, in actual gameplay, these support conversations show up in a NG+ playthrough and you can build them up to C rank through record keeper battles and having them fight with each other. However, once you get up to C rank and attempt to view the conversations, the game informs you that you can't view support conversations and progress the rank if they're not both in your active army. Which is impossible as the three are never playable together.

Well, except for in Zahras. So I got them up to C rank and progressed the game (in Azure Gleam) up to the Zahras chapter, but I still couldn't view them, because Edelgard and Claude don't actually join your party. I tried viewing the conversations the normal way by simply talking to each of the house leaders, but this didn't do anything regarding their support ranks either. So I'm curious. Has anyone found a way to unlock these supports? If not, does this hint at some kind of DLC? Why would they even code these conversations as supports when they could have just as easily made them regular events? I mean obviously I'm not actually missing out on these supports because the game forces you to view them if you recruit Byleth, but it bothers me to see a dull blue "C" with a lock next to it instead of a bright green one.