That's strange since the Greek Orthodox website says the exact opposite.
PHOTIUS' ENCYCLICAL TO FIVE PATRIARCHS OF THE EAST (866) Patriarch Photius of Constantinople was an outstanding hierarch and leader who as a layman was elected patriarch by vote of the people and ecclesiastical authorities. He brought order to the Church and increased its missionary work, especially in Bulgaria. What became another major source of the teachings of the Church is the encyclical epistle of Photius sent to the Patriarchs of the East, with the consent of the Synod of Constantinople, protesting against the innovations of Pope Nicholas I of Rome: his interference in the affairs of the newly-converted nation of Bulgaria, the addition of the filioque phrase in the Nicene Creed, the issuing of the Pseudo-Isidorian Decrees and the Pseudo-Constantian Gift. This encyclical of Photius restated the correct teaching of the Nicene Creed, opposing the filioque phrase; correctly asserted the canonical jurisdictional order of administration of the Church; reaffirmed the correct teaching against the primacy of the pope, his infallibility, the riches of Christ and the saints, indulgences, purgatory, the Immaculate Conception of the Virgin Mary and her bodily assumption. All of these innovations of the West were among the factors which ultimately led to the Great Schism in 1054, setting the stage for the Protestant movement in 1517 as well. Photius' great encyclical restated and reaffirmed the orthodox teaching of the Undivided Church, and stands as a major source of Orthodox teaching.
That page is amazingly anachronistic. The treasury of merits? That wasn't even formulated until the scholastics. St. Nicholas I never added the filioque to the Creed, etc. If you look up St. Photius' actual letter you won't find that stuff in there. The Immaculate Conception was unknown to the West in the ninth century.
Moreover, your cite claims that St. Photius wrote against the bodily Assumption of Mary!!!!! Surely you know how incorrect that must be.
But citing secondary sources against each other is not really going to work, is it? I'll drop you a note if I get a chance in the future to look over +Photius' homilies on the Annunciation and the Nativity of the Mother of God which Fr. Kucharek cites as teaching the Immaculate Conception.