I worked for the resistive systems group from 1976 to ‘81. Yes, some of that data was generated in house but it was not for publication at the time, they were trying to figure out how to use commercially available packaging methods (ceramic dips, TO-3 cans, etc) and keep the thermal emf as low as possible. AFAICR, most of the info came from existing commercial sources. What I find ironic is a common material they struggled with, Kovar, isn’t on the list.
They were keenly aware of the issues since a recent change (at that time) to the primary product, the S102 was improved by eliminating the flexible interconnects between the tinned copper leads and the foil based element. That design change remains in place with the S102C today where the interconnect leads are directly welded to the foil, eliminating one dis-similar metal junction.
As already mentioned, best to measure it yourself under the exact conditions of use.
PS. I assume this the Fluke document you’re referring to?
http://download.flukecal.com/pub/literature/p18-21.pdf