I saw this video earlier today, and while I agree with some of what he says, he is off base in some ways. For instance, I always get more noise if I have to increase "exposure" in Lightroom than if I correctly expose in camera. So, I have yet to see a camera that is really "ISOless." Similarly, you can blow out whites in camera and never be able to get detail back.
I do think that camera manufacturers fudge their ISO numbers, and I can tell you that my D500 exposes darker at the same settings with the same lens compared to my D7200.