I mean, we know they are 4 (5?) travelers who comes who knows why on these parts.
But why are they in the truce or even in the video?
Is there any explanations?
Because it does look like they came and meddle into a war between several others sovereign nations and should be executed on the spot.
The wulin are a faction in game mechanics alone. We don't have a time point in which they have arrived and how long they've been around AFAIK. They were deserters. Not people coming in to budge on territory. Hence why we have just now only gotten a single Wu-lin map. I'd imagine they will be more officially in lore related stuff once the devs get around to adding them in the faction war.