They don't explicitly say it, but the things they have to say about ecumenical councils seem to imply that they share the belief that I have seen elsewhere that the Second Millennium councils Catholics hold are not ecumenical because the Orthodox are not involved, which entails a strange and rather innovative definition of what constitutes an ecumenical council. Certainly it is a definition we do not recognize, even though they claim to accept the same councils as we do.
Can you elaborate on this? Why wouldn't the Orthodox understanding of ecumenical councils necessitate Orthodox involvement?
Most certainly we would require our own involvement. My point of view more relates to the concept that the East and West are separate parts that must be reunited for a council to be properly ecumenical. To complete the analogy, to agree to the Old Catholic definition we would have to think that Rome must be included for a council to be ecumenical, which is not a view held by Orthodox Christians. Indeed, some call the Palamite synods of the 1340s the Ninth Ecumenical Council (though this is a minority view).
From our perspective, an ecumenical council is a council of the
Ecumene, or the Roman Empire. The Seven Councils were all called by the Emperor sitting on the throne of Constantinople. We cannot call an ecumenical council now, not because we are lacking something, for the Church lacks nothing, but because the imperial throne wherein the authority to call the council is vested lies empty.
Pan-Orthodox synods can still happen, and they can decree things for the entire Church, but none of them will be numbered among the ecumenical councils. And it honestly doesn't matter that much. We have had dogmatic pronouncements from various second millennium councils, e.g. Blachernae 1285, Constantinople 1351, Jerusalem 1672. The idea that it's not dogmatic if it isn't said in an ecumenical council just isn't a thing in the Orthodox Church.