I am looking through the breaking changes for Silverlight and I saw this and just about kvetched. Glad to see that some people at Microsoft are just as confused about versioning schemes as the rest of us. This is the Version Detection section from the Silverlight changes document verbatim:
Silverlight 1.0 Beta and 1.1 Alpha will follow this versioning scheme:
Silverlight.js contains a “version” property that checks for the proper version and directs users to the install location if the proper version is not installed.