As someone on the receiving end of POSSE, who is often on the multiple platforms people post to, this approach ends up feeling impersonal and spammy. I totally get the reasoning people have for doing it. But, to me, it's very "ship it" focused, rather than conversation focused. Maybe I'm just getting old.
Can you elaborate? What is impersonal about it? It's more like the opposite: Author doesn't force a reader to choose a specific platform.
atproto feels like a move in the right direction for personal publishing that makes content discovery easier withtout the need to post to multiple channels / platforms. https://standard.site/ is one initiative working towards making this a reality.