The churches teaching on the death penalty is definitely of the authentic magisterium. The church has the authority and the duty to comment in a non-infallible way on the use of the death penalty. The use of the death penalty is undisputedly an area of faith and morals.
No one has disputed that it is part of the magisterium.
These post 1995 teachings have never been non-fallible and there is no Church authority that says they are.
They are, in fact, a wrongly considered prudential judgement, where the facts conflict with the Church’s conclusion. Multiple Church sources have confirmed that any good Catholic may disagree with the post 1995 teachings and remain a Catholic in good standing.
If you look at the foundation, “defense of society”, that becomes clear.
Defense of society is based upon secular systems of ever changing criminal justice policies, worldwide, with wildly divergent degrees of success and failure in protecting innocents from unjust aggressors.
How could any Church teaching, based on that amorphous a foundation, ever be non-fallible? I don’t see that it can be.
Aren’t all Church teachings based in morals and faith, ultimately, if not clearly?