Maybe there should be a separate Module::Build::API document that documents the "producer" API, which far less people care about. I guess you'll think of this as a feature request, or a bug report, and it should thus go onto RT, or on some list.

If I recall correctly, this very thing has been discussed on the list. There may have even been a call for a volunteer.

Update: Here is the thread I'm remembering. These changes are in the development version 0.27_01.