Thanks for the detailed reply. I've not looked much into the theory behind Heyser's time delay spectrometry and related techniques. Looks like I have some reading to do 
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.I believe the poster was pointing out that REW is capable enough to replace a number of special-purpose commercial measurement/analysis programs. Arguably not directly relevant to this thread, though it did serve as a prompt to explaining why someone might want to write their own tooling (which was unclear to some readers). I have no idea where the "marketing" allegations came from...
