Then we are going to disagree, because you seem to think its OK to use Bruno as a point proving JC is wrong with his measurements, and then want to say Bruno is wrong to suggest that JC measurements do have a use.
Well, one way a measurement can be incorrect is due to measuring the wrong thing. In this case, let's assume for the sake of argument that the source of the discrepancy is entirely due to this ground loop issue, as Bruno seems to be assuming. This ground loop is within the test setup itself. But the idea of a test is to measure the device under test, not errors of the test equipment itself. Therefore, the test is in error because it's unduly influenced by errors within the test equipment. However, as Bruno points out, such ground loops also exist within real audio systems too as a rule, rather than the exception. So if we assume the ground loop is the cause of the distortion discrepancy (I seriously doubt this BTW), then the measurement that's unduly influenced by the ground loop is not useless because it demonstrates that the same phenomenon can occur in real audio systems, which are subject to the same kinds of ground loops. I can see where he's coming from, but this conclusion is based on assuming the ground loop really is the cause - and we don't know that because there has been no controlled experiment demonstrating this. It is, as you say, a "plausible cause", but it hasn't been demonstrated to be the actual cause.
Anyway IMO what your saying does not necessarily tie in with Bruno's last post I quoted.
I'm going by his measurements, not by his hypothesis of why the measurements might be different.
I guess we had different perspectives on the validation process and what they actually thought in the end (which Bruno summed up nicely).
But I Still cannot understand how you can equate the AP testing to being identical to what JC did, even Bruno acknowledges they are not the same.
Well, they should have the same results, but they do not. Therein lies the problem.
In other words the measurements your using to prove JC wrong mean nothing as they are different environments, not sure how many times I can quote Bruno on this.
As mentioned, a necessary condition for getting a correct measurement is to get the same answer with two different test setups, within the accuracy of the instruments involved (which is established by calibration). What Bruno's calling the "environment" is really the test equipment itself. But one does not want to be measuring errors in the test equipment, but errors in the device under test. What Bruno is saying is true, but if errors in the "environment" (the test equipment) are dominating the results, that's a problem with the measurement. It's an error.