What's the purpose of fetch mode, as opposed to streaming mode? Is it a legacy of bygone days that just hasn't been deprecated, or is there something I don't understand from reading https://www.postgresql.org/docs/14/app-pgbasebackup.html?
Your backup can go to a single file with it, which it can't do in streaming. Which means it can also be sent through a pipe.
But isn't the whole purpose of pg_basebackup (running it on Node B, when the database instance is Node A)?
It also needs one connection instead of two to the server, if that's limited.
It's 2024, not 2011. Who can't spare an extra connection?