(Excerpt below from from: Doctrine | From East to West)
Is it true that the Eastern Catholic Churches are allowed to have different theological expressions? If so what does it involve?
This certainly is true. The Eastern Catholic Churches are not only “allowed” but are actively encouraged to cultivate their own distinctive theological expressions.
Eastern Catholics, while fully Catholic and in communion with the Pope, differ in more ways than just liturgy. We also possess a unique spiritual tradition, as well as a unique theological approach. While we agree with the Latin Church on fundamental matters of doctrine, we approach doctrine in a very different way – from the Eastern perspective. While the Western Church has traditionally formulated doctrine in terms of scholastic Latin theology, we rely almost exclusively on the theology of the Eastern Church Fathers. This difference, rather than rupturing the unity of the Church, further expresses the true UNIVERSALITY of Christ’s Church.
This is authoritatively taught by the Second Vatican Council:
“All in the Church must preserve unity in essentials. But let all, according to the gifts they have received enjoy a proper freedom, in their various forms of spiritual life and discipline, in-their different liturgical rites, and even in their theological elaborations of revealed truth,” (UNITATIS REDINTEGRATIO, no. 4).
Excerpt above from Doctrine | From East to West
Certainly Opus Dei, as the first Roman prelature approved by the Vatican, has different theological perspectives on Vatican II than traditional Roman Rite/Church theology.
Given the above, it should be perfectly reasonable that a Vatican II Rite/Church with its different theological perspectives can co-exist with the 22 other non-Roman Rites/Churches in union with Rome.