Thats really off topic. There is no need to discuss that further here. This is about post schism saints on Eastern Catholic calenders.
The post schism saints were mistaken, though in many cases it was impossible to even find a Catholic church for many of them, especially if there were monastics or hermits. St. Isaac of Syria, ,a member of the Assyrian Apostolic Church ,is venerated by Catholics, Syriac Orthodox(miaphysites) , Assyrians,and by Eastern Orthodox. Infact Eastern Orthodox consider him one of the greatest spiritual fathers (as I do myself). So Isa, if its muddying the waters to venerate saints who were not of the same Faith then why is Mar Isaac held in such high regard within your own church?
Not that Orthodoxwiki is a valid source but, this is a quote from it on St. Isaac.
"His inclusion is thus an indication that the Church does not regard canonical boundaries as being the litmus test of Orthodoxy. "
orthodoxwiki.org/Isaac_of_Syria
Your answer comes, of all places, from the CE
A Nestorian bishop of that city in the latter half of the seventh century, being consecrated by the Nestorian Patriarch George (660-80). Originally a monk of the monastery of Bethabe in Kurdistan, he abdicated for unknown reasons after an episcopate of but five months, and retired to the monastery of Rabban Shapur, where he died at an advanced age, blind through study and austerity. Towards the end of his life he passed under a cloud as his Nestorian orthodoxy became suspected. He was author of three theses, which found but little acceptance amongst Nestorians. Daniel Bar Tubanita, Bishop of Beth Garmai (some 100 miles south-east of Mossul), took umbrage at his teaching and became his ardent opponent.
The precise contents of these theses are not known, but they were of too Catholic a character to be compatible with Nestorian heresy. From an extant prayer of his, addressed to Christ it is certainly difficult to realize that its author was a Nestorian.
newadvent.org/cathen/08176a.htm
Does the Nestorian/church of the East venerate him?
St. Isaak’s glofication differs from the canonization by
“natural piety” by the indifferent. There are other examples: the work “the Spiritual Combat” of Lorenzo Scupoli being adapted by St. Theophanes and St. Nicodemus for the Orthodox.
Then’s there’s oddities like St. Jerome, whom, I think I’ve stated plenty of times I dislike, although my own priest is quite a fan (he says his personal prayers in Latin, to give an idea of his mind). Jerome was of course pre-schism, but I have seen dates of his canonization as post-schism. The Orthodox don’t question it, nor saints like Popes Victor, Leo, and Gregory, who show Ultramontanist tendencies, while the Vatican canonized the like of St. Meletius, who spent his “career” in defiance of Rome’s rejection of him and fell asleep out of communion with Rome.
Right now we and the Oriental Orthodox are working through the various saints of each other, to see the context of how saints who opposed each other’s communion can be in the same Church. There of course is precedence in the Universal Church canonizing both SS Cyril and John Chrysostom, the former refusing to commenorate the latter (as Jerome did refuse) , saying he was a Judas.
