When viewing official specifications it's always a good idea to check that you're looking at the latest version and that it is an actual recommended implementation and not just a draft.
The version you're looking at is marked as a Working Draft published in March 2001 - this means that it's 1. not a finalised version, and 2. rather old.
It even states:
This draft has been produced by the CSS working group as part of the style activity. It is a public W3C Working Draft for review by W3C members and other interested parties. As a draft document it may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use W3C Working Drafts as reference material or to cite them as other than "work in progress."
Right at the top there's a couple of links. One of these take us to the most up-to-date version:

That particular version (http://www.w3.org/TR/css-style-attr) was published in November 2013 and is a Recommendation. This means it's 1. a lot more recent, and 2. no longer just a draft, but actually recommended to be used.
This version states:
This document has been reviewed by W3C Members, by software developers, and by other W3C groups and interested parties, and is endorsed by the Director as a W3C Recommendation. It is a stable document and may be used as reference material or cited from another document. W3C's role in making the Recommendation is to draw attention to the specification and to promote its widespread deployment. This enhances the functionality and interoperability of the Web.
This latest version doesn't feature the syntax you're wanting to use.