Rather than wade into each detail, let me deal with my suggested techniques more globally. I don't think that a WG can "forbid" any kind of claim by a vendor, just "disclaim" them. This is done by making a statement in the spec, probably in the Conformance section, about the wording of the claim. When a vendor makes a forbidden claim, other parties (e.g., their rivals) will cite the prior published wording of the spec to say that the claim is bogus. The WG stays out of the business of commenting on the claims after they are made.

Here's an example of what might be a "wording of the claim" for the XFoo 1.0 spec:
A properly-formed conformance claim will state:
        1. The version number of the Recommendation...
        2. The date of the errata document...
        3. Which modules are implemented... [assuming XFoo has modules]
        4. Which choices were made on all the implementation-dependent and implementation-defined items in Appendix D, preferably by using the Pro Forma outlined in Appendix H.
        5. The nature of any extensions implemented...
        6. The version identifier of the W3C conformance test suite applied...
        7. Sufficient details of how the tests were applied to allow re-running of the test suite in an independent test environment. These details must show that the test suite was applied in accordance with the instructions provided at [reference]...
The W3C hereby disclaims any assertion of conformance that does not provide all the above information. Furthermore, the W3C disclaims any assertion that passing all the tests in the suite adequately confirms conformance, that passing some but not all tests constitutes adequacy of any kind, or that when two implementations each pass a different number of tests but not all, there is any implication of the relative merit of the two implementations based solely on the number of tests passed.

Notice that the last part is the technique by which incomplete conformance claims are undercut by the WG. To implement my suggested technique #7, the following paragraph would go on to suggest how a buyer can incorporate wording in their RFQ. (e.g., Responding vendors must submit a conformance report that contains all the material required in Section 7.4 of the W3C XFoo 1.0 Recommendation at [URI] and gives pass/fail results for each test in the W3C XFoo 1.0 test suite Version 1.23 at [URI].)

I provided a lot of techniques because I thought that they were supposed to give the WG ideas about how they would "control" conformance measurement and claims. Some could probably be collapsed if too many techniques is seen as a bad thing.

And one I'll deal with individually:
>> 5. For each discretionary item that is a choice, name the items and
>> the choices. A questionnaire should ask which choice was made by
>> reference to the keywords. (Example: when more than one template
>> matches, do you raise error DE16 ("raise-error") or choose the last
>> template and continue ("choose-last")?)
>
>If there are discretionary items, provide a way to identify them in the
>conformance claim.

The identification of them is way more important for test suite management than it is for the conformance claim. Other than that, your tersification of what I wrote is correct. Perhaps the long version can go somewhere else as a technique, then the conformance-claim discussion can point at it:
If there are discretionary items, use their identifiers (see GP x, Technique y) in the conformance claim.
.................David Marston