Nod. We do have some weirdness there. The schema is that packages built from postgresql itself use postgresql-*-x.y (mostly), and all others use postgresql-x.y-*. Arguably, that's confusing.
I have some plan in the back of my brain that extension modules should ship .so files for all postgresql versions they support in one single binary package. That would get rid of most of the versioned packages with minimal space overhead (the .so files are usually pretty small, with lots of common files in /usr/share).
