>>4446080
I agreed with you up until very recently, and I suspect now that the RPX 100 and 400 films used to be something different before switching to Kentmere rebranding.
These frames are the same shot on RPX 400 and Kentmere 400, with the exposure settings on the RPX scan carried forwards to K400. They're identical. The negs also are virtually the same, a smidge more density in the Kentmere but nothing meaningful.

I did my own testing because I was very dubious as well but the facts speak for themselves