I'm curious how much of the underlying pgsql storage engine was rewritten since Aurora/MySQL uses a completely different engine than the default InnoDB.
They need to disable some features to make concurrent readers on the same network disk work. I'm sure it's harder than I'm making it sound, but I don't think it's a new storage engine beyond the disk level.
If so, though, hopefully there's a silver lining of faster incorporation of new pgsql features into the Aurora/PG service.