W3C and other standards organizations are in the business of defining languages — conventions that organizations can choose to follow — and not in mandating operational behavior — telling organizations and participants in the network how they are supposed to behave. Organizations (implementors, operators, administrators, software developers) are free to choose which standards they adopt, and what their operational behavior will be.
In some posts on the www-tag mailing list, I was trying to point out the risks in defining languages such that the "meaning" of the language depends on operational behavior. In some ways, of course, this is a fallacy: in general, what an utterance "means" in some operational way depends on what the speaker intends and how the listener will interpret the utterance.
However, as an organization, W3C can, and should, define languages in which the meaning is defined in the document, in terms of abstractions rather than in terms of operational behavior. The result is more robust standards, those that have wider applicability, that can be used for more purposes, and that create a more vibrant and extensible web.