Josaphat Kuncevyc was a great proponent of the Unia who was killed by Orthodox believers by being hit with a halberd, shot, and then thrown into a river. Most hagiographies you read of him are as you might expect stridently anti-Orthodox. The treatment of him by Orthodox is no less severe (see here). Even today his name is used to polemical ends (see here). All that to say celebrating a Divine Liturgy at the Vatican Basilica of St. Peter on St. Josaphat's feast day is not an innocuous or irenic move.
(RISU) - The patriarch Sviatoslav (Shevchuk) on 25 November with the special permission of Pope Francis led a solemn Pontifical Divine Liturgy at the altar of the Vatican Basilica of St. Peter on the occasion of the 50th anniversary of the laying of the relics of St. Josaphat, martyr for Church unity.
Cardinal Leonardo Sandri, Prefect of the Congregation for the Oriental Churches, almost all the bishops of the Synod of Bishops of the UGCC, Bishop Milan Shashik, Bishop of Mukachiv Eparchy, representatives of other Churches sui iuris and the Apostolic See.