That is not true. The drawing that was posted by @subtec was posted in [H] and Jeff specifically said that it was the most current drawing from the same model that he gave to the manufacturers. He only posted those to disprove Necere who found out that the components that are claimed to fit in the Project mATX can't fit in the volume that is advertised:
Jeff advertises 70mm of space for a top radiator and five slots. That is both correct, but that already puts the height to 329.905mm, not including panels and clearance for the GPU. The advertised height for the case is 327.8mm. Manufacturing tolerances for sheet metal bend-to-bend dimensions is usually 0.25mm. It is absolutely clear that Jeff is not giving out the correct dimensions of the case, there is no way around it.
This is certainly better than the dimensions being correct and the advertised parts not fitting, but it is still false advertising, and even after this was pointed out to him, he didn't change it. I understand this is being done to stay below the magical 20L mark, but it's a very shady move to make. He could've just said it was a mistake, but after a lot of arguing, it has to be assumed that this false advertising is a willingly done to put his product in a better light. I don't have to tell you that that's illegal and competitors could sue him for it.