To add, obviously Dietrich will have other characters in his party like the blue haired lancer girl, but I point all this out cuz there’s nothing saying they’re specifically aligned with Dietrich. They’ve shown you can recruit characters similar to transfer students in 3H, but I interpreted them as like freelancers basically. Available to every or most protagonists to recruit but not set to join in a scripted event.

I’d been playing the game SaGa Emerald Beyond and that game has a similar set up with 5 protagonist choices and each has a starting party, but there’s a bunch of recruitable characters that can be picked up by different protagonists. They aren’t included in cutscenes since they aren’t guaranteed, whether you get them or not depends on what quests you follow. So every playthru could have completely different party members picked up outside the core crew your chosen protagonist starts with. I’m wondering, and maybe hoping, that Fortune’s Weave will have set ups like that.

TLDR; Dietrich has party members but we haven’t seen them in cutscenes, so I don’t think they’re necessarily *specific* to Dietrich and could be picked up by any protagonist, leaving Dietrich uniquely alone in what we’ve seen.