I think its more like co-op than live service. You can play with 2 other people. I think they also adjusted it for 2 player co-op.
Well night reign fits more the term of a live service than shadow of erdtree, did I miss something ?
Discussion
Yeah but you can't deny that thing about close in to the center of the map is very Fortnite thing to do lol in tha sense plus, night reign is much closer to a live service, since it's likely going to get a DLC