I also raised the idea of using a top-level typealias in the pitch thread on controlling default actor isolation, based on the (albeit little used) feature where the default type of literals can be changed within a file.
IIRC, a fileprivate
typealias in the literal case only affects that file, not the whole module. I didn't realize Distributed also used a top-level typealias for something like this, and that just points to even more precedent for expressing certain type-based defaults in this manner.