empty authority or empty reg-name?

In the current draft of 2396bis, sections 6.2.3 and 6.3 talk about an
empty authority being equivalent to localhost, while section 3.2.2 says
an empty reg-name should be equivalent to localhost.  Which is it?  Is
foo://a@:2/ supposed to be equivalent to foo://a@localhost:2/ ?

AMC
http://www.nicemice.net/amc/