I've seen a couple of these "distributed" postgres extensions.
My question is, has any of them been talked about being upstreamed to postgres itself? Or, adding a custom built in feature to postgres itself?
This is not an extension, it's a proxy! Very different. You can deploy it anywhere already without having to wait for upstreaming or your cloud provider adding support for it. It's one of the two reasons why we built it this way, the other being performance (it's much faster to do this in the proxy than inside Postgres).
It doesn't actually distribute postgres. It lets you use one connection to talk to multiple postgres databases by switching between them and if you're very careful you can sort of see it like a single database, ht it's not really.