I don't exactly keep up with all the changes between one version of the HDMI spec and the next but this is how specifications work (I work in software standards, in other words implementing specifications):
The spec defines the interface (in the HDMI case both the physical hardware interface and the software interface) and which features should be supported. Specs generally contain should, may, and must when defining certain features or interfaces. Must is self-explanatory. Should is optional but a strong recommendation whereas May is totally optional.
So a given implementation of said spec may not be the same as another. You cannot say HDMI 1.1 means this and HDMI 1.2 means that. The spec defines the gamut of what must, may, and should be implemented. One vendor's HDMI 1.1 implementation may or may not implement the same feature in the same way or implement it all - as long as the implementation falls within the 'rules' of the spec it is compliant. Why do you think interoperability often falls short of the ideal?