It's not a question of private opinion. First of all, it's a simple question of objective reality -- "all" and "many" are 2 different words that mean 2 different things. Secondly, the Church has already spoken on the subject:
Catechism of the Council of Trent
"The additional words for you and for many, are taken, some from Matthew, some from Luke, but were joined together by the Catholic Church under guidance of the Spirit of God. They serve to declare the fruit and advantage of His Passion. For if we look to its value, we must confess that the Redeemer shed His blood for the salvation of all; but if we look to the fruit which mankind received from it, we shall easily find that it pertains NOT UNTO ALL, BUT TO MANY of the human race. When therefore (Our Lord) said: For you, He meant either those who were present, or those chosen from amoung the Jewish people, such as were, with the exception of Judas, the disciples with whom He was speaking. When He added, And for many, He wished to be understood to mean the remainder of the elect from among the Jews and Gentiles.With reason, therefore, were the words For All NOT USED, as in this place the fruits of the Passion are alone spoken of, AND TO THE ELECT ONLY DID HIS PASSION BRING THE FRUIT OF SALVATION. And this is the purport of the Apostle when he says: Christ was offered once to exhaust the sins of many; and also of the words of Our Lord in John: I pray for them; I pray not for the world, but for them whom thou has given me, because they are thine.
Well, many can also mean all men. St. Paul, after all, says:
For just as through the disobedience of the one man the many were made sinners, so also through the obedience of the one man the many will be made righteous.
In which he surely means the same as he says in that same chapter of the epistle: "sin entered the world through one man, and death through sin, and in this way death came to all men, because all sinned".
And since this seems so, it doesn't seem impossible that the words should mean two different things at the same time, just as "the rock" means both St. Peter and his confession of faith.
Secondly, the Church has already spoken on the subject:
The Catechism is referring to the traditional rite. It is obvious to all that it is permitted to the Church to modify the words of consecration, so long as the form expresses the grace which the Sacrament effects and signifies: the variety of different rites makes this clear, especially the addition of the "mysterium fidei" to the Roman liturgy.
So I don't see any impediment to understanding that Rome has added the sufficiency of Christ's Passion as at least a secondary understanding of the words "pro multis" in the reformed rite, which can be proved from the Roman approval of the translation "for all".