That is why particular types of film scholars (such as David Bordwell) will not explicitly acknowledge "noir" as being separate from the Hollywood product from which it emerged in its American incarnation. That nebulousness remains intact for as long as American noir is considered the point of origin for defining concepts.
This entire effort smacks of a variation of American exceptionalism, and it's been aided and abetted by the Cahiers du Cinema crowd who fetishized Hollywood films with a violent edge, as if violence (physical or emotional) could be made into an end unto itself. That has cemented in place a narrative about noir that allows adherents to play it both ways in terms of analysis--exalting "noir" as a mythical zeitgeist with interlocking cosmic rules and traps, but also being able to demean or minimize it as mere "genre film" when it becomes too formulaic. But as Dan notes, and Bordwell prefers to emphasize, there is a parallel force in dark films that wells up as narratives become more complicated and emotional relationships become more intense and complex. Much of this "thriller" impulse is initiated by non-American writers (Daphne DuMaurier, Patrick Hamilton, Joan Harrison) and becomes part of what Bordwell documents as the "novelization of film" that emerges in darkening melodrama throughout the 40s.
But only by discovering and accepting the fact that "noir" originates somewhere other than America can one begin to correct the situation that currently exists. I do not mean "proto-noir" or antecedents that would later appropriated into some American "creation myth": I mean film noir, as practiced by Renoir, Duvivier, Maurice Tourneur, Siodmak and the obscure Victor Trivas (with Pierre Chenal hot on their heels...) in France in 1932-33--films like LA NUIT DU CARREFOUR, TUMULTES, LA TETE D'UN HOMME, AU NOM DE LA LOI and DANS LES RUES. which individually and collectively initiate all of the elements that critics associate with "noir."
But this will be a tough sell for those who are getting the story from current sources. Which is one reason why one needs to remain concerned about Mr. Muller (though, as you note, that can be sidestepped in the effort to provide a revised, more accurate history). And frankly, at this moment in time I'm much more concerned with Mr. Mueller instead of Mr. Muller...
Two books that you might want to consider reading are Bordwell's REINVENTING HOLLYWOOD (which you should find refreshingly jargon-free) and, if you're willing to be a bit adventurous in order to get more attuned to the connections between surrealism and noir, Jonathan Eburne's SURREALISM AND THE ART OF CRIME. The latter doesn't focus on "film noir" per se but several chapters therein connect some interesting dots. And the relations between surrealism, "art film," and noir in France start to become easier to trace as well.
(TOC = Table of Contents)