I understand your point. 1) I was testing a known configuration of the transformer which joins the primary and secondary together on the low side. I could test the transformers with the low sides separated but that is not the configuration that is being sold. 2) There is no inductive connection on either side. The four grounds are common and the connections to and from the S/A are properly terminated transmission lines.
Please feel free to do your own test on any configuration you wish and share your results.