Kolo: the Uniates were never required to add the filioque under pain of anathema. That is just a historical fact. Lyons II condemns those who deny that the Spirit proceeds ab utroque. Where does the 381 Creed do that? Nowhere. Lack of affirmation is not a denial. The Commission recommended that - wrongly, in my opinion - in order to further relations with the Orthodox, who do deny the procession ab utroque.
Pope Benedict XIV says in his 1755 Encyclical Allatae Sunt:
On the assumption that the first two answers are accepted, the third and final question is whether Orientals and Greeks can be allowed to say the Creed in the way they used to before the Schism, that is to say, without the phrase "and from the Son." On this final point, the practice of the Apostolic See has varied. Sometimes it allowed the Orientals and Greeks to say the Creed without this addition. This allowance was made when it was certain that they accepted the first two points, and it realized that insistence on the addition would block the way to union. At other times this See has insisted on Greeks and Orientals using the addition. It has done this when it had grounds to suspect that they were unwilling to include the addition in the Creed because they shared the false view that the Holy Spirit does not proceed from the Father and the Son or that the Church had no power to add the phrase "and from the Son."
The former approach was used by two popes - Blessed Gregory X at the Council of Lyons and Eugenius IV at the Council of Florence - for the reasons already mentioned (Harduin, Collectionis Conciliorum, vol. 7, p. 698D, and vol. 9, p. 305D). The latter position was taken by Pope Nicholas III when he realized that Emperor Michael was not acting in good faith and was not abiding by the promises he had made in establishing union with his predecessor Pope Gregory X. The evidence for this comes from the Vatican Archives and is printed in Raynaldus, 1278, sect. 7. Martin IV and Nicholas IV acted in the same manner. Although the sources are contradictory about the attitude of these popes to this affair, Pachymeres, who was then writing the history of Constantinople, openly declares that they did not imitate the fair judgment of their predecessors. Rather they required that Orientals and Greeks add "and from the Son" to the Creed, in order to remove doubts about their orthodoxy, "to make a definite trial of the faith and opinion of the Greeks; the suitable pledge of this would be for them to say the same Creed as the Latins."
Pope Eugenius IV at the Council of Florence allowed the Orientals to say the Creed without the addition. But when he later received the Armenians into union he obliged them to include it (Harduin, vol. 9, p. 435B) perhaps because he had learned that the Armenians were less averse to the addition then were the Greeks.
Similarly, Pope Callistus III, when he sent Brother Simon of the Order of Preachers to Crete in the capacity of Inquisitor, commanded him to watch carefully that the Greeks said "and from the Son" in the Creed, since in Crete there were many Greek refugees from Constantinople which had fallen to the Turks two years earlier (Gregory of Trebizond, epistola ad Cretans, in his Graeciae Orthodoxae, quoted by Allatius, p. 537, and confirmed by Echardus, Scriptorum Ordinis Sanai Dominici, vol. 1, p. 762). It may be that the Pope suspected that the Greeks from Constantinople were weak in this dogma of the faith.
There is nothing at variance with the decrees of the Council of Florence in either of the two forms of the Profession of Faith which, as We have mentioned, were required of the Greeks by Gregory XIII and of the Orientals by Urban VIII. Constitution 34, sect. 6, of Clement VIII (veteris Romani Bullarii, vol. 3) and Our constitution Etsi Pastoralis, sect. 1, are both addressed to Latin bishops with Greeks and Albanians who observe the Greek rite living in their dioceses. These people should not be ordered to say the Creed with the addition of the phrase "and from the Son," provided that they confess that the Holy Spirit proceeds from the Father and the Son and that they recognize the Church's power of making this addition. They should be obliged to say the additional phrase, however, it its ommission would cause scandal, if this particular custom of reciting the Creed with its addition prevailed in their locality, or it were thought necessary to obtain unambiguous proof of the correctness of their faith. However, both the fathers of the synod of Zamoscia (heading 1, de Fide Catholica and the fathers of the synod of Lebanon (pt. 1, no. 12) were right to prudently decree, in order to remove every doubt, that all priests subject to them should use the Creed with its additional phrase in accordance with the custom of the Roman Church.
Gee, I hate to sound like a broken record, but everything you've written doesn't explain why Roman Catholic theologians, in discussions with Orthodox theologians, which had the authorization to carry on those discussions from the Pope, felt compelled to recommend lifting the condemnation of Lyons II just two years ago.
By the way, unlike FormerLib who only knows "some" Byzantine Rite Catholics who deny the filioque, every single one I know denies it.
The pseudo-Synod of Zamost was an orchestration of the Poles, and it was annulled by Pius XI, as it destroyed the Byzantine rite in Ukraine among the Catholics.
Here is what the Union of Brest had to say:
1. Since there is a quarrel between the Romans and Greeks about the procession of the Holy Spirit, which greatly impede unity really for no other reason than that we do not wish to understand one another - we ask that we should not be compelled to any other creed but that we should remain with that which was handed down to us in the Holy Scriptures, in the Gospel, and in the writings of the holy Greek Doctors, that is, that the Holy Spirit proceeds, not from two sources and not by a double procession, but from one origin, from the Father through the Son.