Maybe thats how feathertail gets to the tribe of endless hunting. Maybe they both have the endmost forrest and its what seperates the two? And like all the oldest spirits are near the center of the forest while the younger old spirits stay towards the fringes of the forest on their respective sides.
I really love your idea that The Endmost acts as some sort of link between those two afterlifes. The ancient cats and Starclan are so inextricably linked in canon, and the Erins never actually explained how they meet up / connect with each other. More ghost magic, I guess.
Anyway, I think The Endmost Forest as a link between the two makes a lot of sense, actually. The Endmost isn’t a place where new souls typically want to go. Why would they, when all of their loved ones have either recently passed or have yet to pass? It would make sense for them to stay and wait, rather than wander alone in an age-old, lonely forest.
Keeping that in mind, how would our protagonists (or the greater majority of other cats in the main-section of Starclan) even know about the link? They don’t actually traverse the Endmost. It keeps a healthy degree of separation between the two.
Or, the Endmost leads to Endless Hunting, but it’s got a barrier-type deal that the Place of No Stars has. Only certain cats can cross over??