I think this gets into the rather confusing catholic vs Catholic thing. I generally reserve the large ‘C’ Catholic for those who are in communion with Rome which I think is the accepted convention and it’s just easier so as to avoid confusion. I use the smaller ‘c’ to refer to those churches that have a credible claim to apostolic origins with orders and sacraments. (Not getting into the debate over valid sacraments, that just adds to the confusion.)
I have no patience with the anti-Catholic bigotry that I see all over, but neither am I fan of doctrinal syncretism or relativism. The One Holy Catholic and Apostolic Church referenced in the Creed is the Orthodox Church, and no other. Where the subject is the Creed it must also be noted that the Oriental Orthodox don’t recite the second part as far as I am aware. For their part the Roman Catholics recite the creed of the Second Council of Lyon (1272-74), which proclaims the double procession of the Holy Spirit, vice the Nicene Constantinopolitan Creed.
I absolutely agree that the differences between the OO’s and we EO’s are not nearly as great as they were once believed. But there are still differences. I also don’t believe any of the canonical Orthodox churches are commemorating any post Chalcedonian saints from the Oriental Orthodox Communion.
Privately I have no doubt of this man’s sanctity. Just as I have no doubt that the 21 New Martyrs of Egypt are true martyrs and saints. For that matter I also have a healthy respect for some of the post-schism Latin saints. But while private veneration is one thing, public veneration is another.
I think that horse has been out of the barn for about 250 years, though -- according to the article it seems that Armenian Catholics have always accorded a public cultus to St. Gregory, ever since their church was founded.
I appreciate that you do this because I thought that the Orthodox posters would say that he was Catholic based on the other "catholic".