[NRx]

In 950 AD, he would have been considered a member of the One, Holy, Catholic Church.

By the Armenian Church certainly. But not by Rome. The Armenian Church broke communion with Rome (and Constantinople) in 554 when they formally rejected the Dyophysite formula adopted by the Council of Chalcedon.

[annalex]

I agree that this is surprising, but since the Armenian Catholic Church venerates him as well, it is safe to assume that nothing in St. Gregory of Narek’s teaching is at odds with the decisions of the Chalcedon.

I don’t see how the late emergence of the Armenian Catholic Church or the fact that Armenian Apostolic Church also venerates him has a bearing on the above. Let’s not forget that most of our saints are common to all authentic churches.