At the core of Vatican II is a completely novel ecclesiology and soteriology. It extends the Church of Christ beyond the visible society of the Catholic Church and refers to an (anti-Tridentine) invisible Church, with a visible core.
This raises an interesting question:
What is the eternal destiny of a 5 year-old Greek Orthodox child who dies in the state of grace?
On the one hand, he is not culpable for schism (or any other grievous sin).
On the other hand, he is not a member of the visible Church.
Since it is absurd that one in the state of grace can be damned, it stands to reason that he is not damned, despite not being a member of the visible Church.
But he
is joined to it by the life of sanctifying grace.
It is for this reason that the distinction between body and soul of the Church is legitimate, albeit abused by Rahnerites (and hence Pius XII's warning about the danger in applying this dintinction).
But it seems to me that one who is joined to the soul of the Church by grace, and is therefore certainly saved, is not outside the Church in the sense condemned by the EENS dogma (because it would again be absurd to contend that EENS by implication wished to assert the damnation of those in the state of grace).
The absurdity is exposed even more when one considers that sanctifying grace is a participation in the divine economy and life of Christ, whereas the primary characteristic of the damned is the deprivation of the Beatific Vision: One cannot simultaneously suffer eternal remorse for what has been lost, while at the same time participating in the life of Christ. I concede that being in the state of grace, and possessing the Beatific Vision are not the same thing, but the deprivation of the latter, amidst maintaining the former after the judgment is certainly an incongruent notion.