One somewhat self-serving justification Intel might make for this claim is that the functional specification does not say anything about the specific behavior that is being used by the exploits.

In addition, functional specifications are sometimes modified to conform to as-built behavior. When used responsibly, this is a reasonable response, and in practice unavoidable for something as complex as a modern processor.

On the other hand, Intel's statements are silent about what implications cannot be found in the effort they and others are putting into mitigating this feature.

Tangentially, the Titanic sailed with the number of lifeboats it was designed to carry.