I just want to note ( to make sure there isn't any confusion) that "Priv 1.11" and "Priv 1.12" are NOT extensions.  They effectively refer to documents that contain a collection of extensions (a superset of the following extensions):

The actual extensions that people are trying to refer to when they say "Priv 1.11" and "Priv 1.12", and their names are:  Sm1p11, Sm1p12, Ss1p11, and Ss1p12.  These are a subset of the contents of the Priv 1.11 and 1.12 documents.

For any ratified extension one shouldn't need to refer to a dated release of the document that contains the extension - since ratified extensions are frozen and any new "version" of an extension must be a separate new extension.  Going forward, version numbers on an extension should be meaningless.

But, to be more precise, the text of a ratified spec is allowed to change only to the extent of incorporating "typo" corrections and clarifications.  To that extent it is useful to look at the latest release of the document containing a ratified extension so as to see the latest typo fixes and clarifications.

Greg