Ah. I didn’t make that statement. The whole thing about “even if the Pope” etc. didn’t seem moot because he’s given no sign of changing it anyway.
I’m not sure that the valid matter of the Eucharist, or indeed any sacrament, would NOT fall under the things of Truth as well as Tradition, anyway. AFAIK, there is no way that the matter of any of the sacraments can or will change, although how they are administered may. For example, baptism can be done as immersion, pouring, or sprinkling, can be done for infants, adults, elderly. . .but the substance needed is always going to be water, and never anything but water. So the way a person gets baptized can change a bit within certain prescribed limits, but the water used will never change.
And with matrimony, the people involved are always a man and a woman, free to marry. They can be married, as Catholics, at a Nuptial Mass or not; their wedding attire, decorations, music etc can be as individual as they like, etc., they can be old or young, but it’s always one man and one woman.
A priest again, old, young, any country, but always a baptized male.
The Sacrament of the Sick AKA Extreme Unction in my youth was always given for those in danger of death. Now the criteria to define that danger has expanded a bit, but it is still given with the oils.
Confirmation can be given with baptism, or at any age.
Reconciliation always involved face-to-face communication, and the proper words by the priest who absolves in the name of the Father, Son, and Holy Spirit. Sometimes we are asked to do a penance but it is not a condition for forgiveness. The main parts, the face to face of priest and penitent (even if the faces were shadowed by a grille, the confession could not be done long distance, by letter, etc.) and the absolution, are there. But we can choose the words of our act of contrition, for example.
The Eucharist can be received in Eastern Churches by children. It can be received on the tongue or in the hand. It can be received under one or both species. None of the ways to receive have any bearing, though, on the matter that makes up the Eucharist.
So to me it seems that the backbone of the sacraments, the matter, stays the same and cannot be changed, but how it is received can be, up to a point, the point being that for example with matrimony, it can never go from being one man and one woman free to marry to two men and one woman, or two women and one man, or two women, or two men. It cannot change the core of the sacrament. And I believe that is the same with the Eucharist: Wheat bread and grape wine.
