I don't think that it was as a favor to Nordost. Their partner in this measuring venture, Vertex, is owned by Steve Elford. Steve produced hifi stuff (cables, power conditioners and racks) as a sideline, and his main business of military contracting finances his "hobby". They were (and still are) a competitor to Nordost. Steve brought some of this finding to Roy Gregory who was the Editor of the UK-based magazine HIFI+ at that time. Roy thought that it was extremely interesting, and when he left HIFI+ and joined Nordost, he convinced Joe Reynolds to finance more investigation.
I know that this smacks of cable company b.s. but when I met the three of them last year, they genuinely thought that they had found a new form of measurement that would advance the science of audio reproduction. They are financing the investigation into cables and power conditioning, but there is no reason why an amplifier company can't pay Acuity Products to measure amplifiers the same way.
The results make it sound simple, but if you've tried recording the output of a CD player and comparing it to the CD itself using Audio Diffmaker you will find that it is a non-trivial task. The biggest problem is synchronizing the sampling to the input - otherwise you are sampling at a different place in the waveform and the comparison is totally invalid.