Just need to understand that the catechism never mentions anything about dying at all, nor, in that particular teaching, does it even mention anything about salvation, or even damnation for that matter. Note that the catechism does not even say that their good intentions and repentance guarantees a state of "grace and righteousness", only that it avails them to it.
We know the catechism would never mean that an unforeseen accident means an accidental death - that would mean the catechism is preaching against the Divine Providence of God, as if the catechumen's death were unexpected or a surprise to God - which is entirely conciliar thinking, used in heretic's attempts to promote a BOD.