That doesn’t say when ensoulment takes place. It says one is destined from conception, but as the Sacred Congregation teaches, that does not mean ensoulment take splace at conception. So, the SC certainly didn’t contradict the catechism. Those guys are far too smart to do that. What they have done is construct a seamless teaching that is consistent through both catchism and SC doctrines.
Here’s an interesting exerpt from article on the topic.
*"They often suppose that the Catholic Church teaches that destroying human embryos is unacceptable because such embryos are persons (or are “ensouled”). While it is true that the Church teaches that the intentional and direct destruction of human embryos is always immoral, it would be incorrect to conclude that the Church teaches that zygotes (a single-cell embryo) or other early-stage embryos are persons, or that they already have immortal, rational souls. The magisterium of the Church has never definitively stated when the ensoulment of the human embryo takes place. It remains an open question. The Declaration on Procured Abortion from the Congregation for the Doctrine of the Faith in 1974 phrases the matter with considerable precision: *
**“This declaration expressly leaves aside the question of the moment when the spiritual soul is infused. There is not a unanimous tradition on this point and authors are as yet in disagreement. For some it dates from the first instant; for others it could not at least precede nidation [implantation in the uterus]. It is not within the competence of science to decide between these views, because the existence of an immortal soul is not a question in its field. It is a philosophical problem from which our moral affirmation remains independent.” **
catholiceducation.org/articles/medical_ethics/me0116.htm
Here is the full paragraph from from the Sacred Congregation from which the above was quoted. I have bolded the text the above author omitted. I figure the full text gives a bit more context.
"19. This declaration expressly leaves aside the question of the moment when the spiritual soul is infused. There is not a unanimous tradition on this point and authors are as yet in disagreement. For some it dates from the first instant; for others it could not at least precede nidation. It is not within the competence of science to decide between these views, because the existence of an immortal soul is not a question in its field. It is a philosophical problem from which our moral affirmation remains independent
for two reasons: (1) supposing a belated animation, there is still nothing less than a human life, preparing for and calling for a soul in which the nature received from parents is completed, (2) on the other hand, it suffices that this presence of the soul be probable (and one can never prove the contrary) in order that the taking of life involve accepting the risk of killing a man, not only waiting for, but already in possession of his soul."vatican.va/roman_curia/congregations/cfaith/documents/rc_con_cfaith_doc_19741118_declaration-abortion_en.html