Barring a reliable source, I think the claim to his Chalcedonian sympathies is bogus. He would not be venerated as a saint by the Armenian Church if he had been defending a theological formula they had condemned. This sounds like something cooked up in an effort to explain why Catholics were being allowed to venerate a schismatic/heretic as a saint. Especially in the years before V-II that sort of thing would have raised a lot of eyebrows.
You make excellent points.
I think you may be on to something here. It is my understanding that Gregory of Narek was not included in the Roman Martyrology until 2005. Prior to VII, he is not to be found in the Roman Martyrology of the Catholic Church.