I've an opportunity to have a look at the catechism, and, yes, I don't see how any Eastern Catholic could object to its assessment of the Councils, early and later Latin.
The rejection of the later four by the Orientals was based on their rejection, as heretical, of the Churches that participated in them. As you know, the Robber Synod of Ephesus was convened to fight Chalcedon's definitions of the Nature of Christ. The Oriental Orthodox were quite serious in regarding the later four councils as "Byzantine local Councils" and, indeed, heretical since they were excommunicated etc. Same for the Assyrians. Communication would not have mattered - perceived and condemned heresy did.
You raise a number of fascinating issues having to do with the Roman procedure for "receiving back" Churches.
Florovsky mentions the Roman method at one point and he accurately summarizes it.
At the Union of Brest-Litovsk, and I daresay all other "Unias," a part of the Kyivan Church was recieved into union with Rome. Rome certainly saw this as a return to its fold from which this Church was removed definitively in 1054 - although Roman polemical writing later tried to show that Kyiv never "really" separated from Rome.
As a condition of such a union, Rome did not insist that all local Orthodox saints be removed from the calendar - indeed Sts. Volodymyr and Olha were not only allowed as local saints of the Ukrainian Catholic Church but were later placed in the universal Roman calendar, along with Boris and Hlib.
But Rome insisted that Orthodox saints who were known to be "Anti-Roman" be removed from the calendar of the new Eastern Church united to Rome.
In fact, in the case of Brest-Litovsk, no such saints were removed. St Photios was venerated at Constantinople at the time ONLY and his cult was not everywhere present as a liturgical cult, nor did it need to be.
The Saints of the Kyivan Caves Lavra were likewise only local Saints of that Monastery within Orthodoxy at the time of the Union of Brest-Litovsk, save for Sts. Anthony and Theodosius.
It was only later under St Peter Mohyla that this choir of saints was canonized for the Kyivan Church and later this was expanded for all of Orthodoxy, although they are not in most Greek calendars.
So the Kyivan Church retained all of its Orthodox patrimony with respect to the saints and icons that it had at the time of the Union of Brest.
Met. Andrew Sheptytsky, in 1904, received a decision from Rome with respect to the Orthodox saints capable of Catholic veneration by the Russians coming into union with Rome. In that calendar, Photios was definitely expunged, as were Mark of Ephesus, Gregory Palamas (now recognized by Rome as a saint) Athanasius of Brest (who condemned the unia violently and whose feast day is tomorrow) and some others.
Rome has never approved of the cult of St Photios, even though there is no censure of him within Catholicism any longer (despite what the tradlats on EWTN say).
In our case, anyway, he was never expunged simply because he was never on the local Kyivan calendar to begin with.
In the late 19th century, the Austro-Hungarian Empire DID insist the Ukrainian Catholics expunge certain icons (Pochaiv) and popular Orthodox saints from their calendars for fear of Russification etc. Patriarch Josef restored these later.
Yes, I agree most readily that the issue of a council's ecumenicity has nothing to do with the orthodoxy of its theology or its authority.
And I don't know under what conditions the Ruthenian Hierarchs understand their union with Rome to be.
The documents of Brest-Litovsk indicate the formal recognition by the Orthodox bishops who signed it of the Pope's authority over them whether delivered personally or in Ecumenical Council.
No mention, in fact, was made of any authority of a local Latin Council, which, as the Council of Trullo and its aftermath indicated, sometimes had the force of a universal council.
The Kyivan bishops were only obligated to recognize the Pope's direct teachings on faith and morals whether stated personally or in Ecumenical Council.
That was a tacit recognition of the later 14 Councils presided over by the Pope.
So, as far as our Particular Church was concerned, it had less to do with our participation than it did with the fact of papal ratification as an ecumenical council. It is such because the pope says it is, period.
And the Kyivan Church did not participate, nor could it have, in the deliberations of all of the early seven Councils, yet that did not mean they were not ecumenical for the Kyivan Church in union with Constantinople. If it were in union with the Syriac Orthodox, then the first three would be THE normative number of Ecumenical Councils.
And to say we accept the later 14 councils but reject that they are ecumenical is really a contradiction.
Rules and regulations about Latin Church ritual and discipline certainly don't apply to us.
But if all 14 councils are proclaimed ecumenical by the Pope to be upheld by all Catholics, then that includes us too.
Again, it is not whether we affirm their ecumenical nature, but that the Pope certainly does. To say that our acceptance of them as ecumenical is "Latin" is a conclusion that is not held by those who do not share it.
We all have our "limus tests" of what we consider to be "Orthodoxy."
But just as long as we don't go so far as to be outrightly contradicting Catholic doctrine along with Latin Church imperatives.