Dear DJE,
Only JLC has a history of true manufacture. Members of the grand three (PP, VC, and AP) do not have such history. VC is no exception.
Therefore, writing, as you did, that "Vacheron Constantin is not historically a calibre maker..." needs some balance and should be put into proper perspective, as it seems to imply that PP is historically a caliber maker. Which is not quite true. (I know, you did not say that, but the conext clearly implies it.)
Case in point is that all PP chornos prior to now used either Valjoux or Lemania movements. Because Valjoux and Lemania were specialist in chrono calibers and made the best designs.
(There is really too much froth whipped up nowdays about the "in-house" movements, as traditionally Swiss watch makers relied on the specialist caliber designers and makers.)
AJ