some things are true that never happened and some happened, but are not true.
Being a newcomer, I wonder whether the link has already been made by revisionists between the truth finding techniques of Holocaust research and the 'consensus based' anti-Popper paradigm known as post-normal science (PNS), introduced by Funtowicz and Ravetz during the 1990s, and supported by Frankfurt school acolytes like Habermas, where scientific goals should be controlled by political or social actors.
It basically states that classical scientific truth finding through experimental verification/falsification of theses ("normal science") must in certain cases be replaced/complemented by consensus-oriented global peer review processes ("post-normal science").
Thus theses are not verified by observing reality, but accepted or discarded by a set of "mainstream experts" committed to humanity.
Apart from the "Holocaust", this concept of science can currently be seen at work in many health related dogmas and, of course, in the Man Made Global Warming discussions.
Being more recent than the "Holocaust" historiography, post-normal science philosophy may even have been triggered by the success of the narrative.