CathInfo.com

There are differences between the Missals of St Pius V, Clement VIII and Urban VIII.

To give an example:

In the 1570 Missal after the Words of Consecration of the chalice the priest elevates the chalice whilst saying Haec quotiescuмque whilst elevating the chalice.
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In the Clement VIII Missal the rubric is changed and the celebrant says Haec quotiescuмque after placing the chalice back on the corporal and before genuflecting and then elevating the chalice:
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However, Clement VIII continues:

"We have also entrusted some of Our Venerable Brethren, Cardinals of the Holy Roman Church, versed in Holy Writ and skilled in ecclesiastical antiquity, with the business of restoring the Missal to its primitive and purest form. In their loyalty to Us, and in their piety and devotion to the Church, these Cardinals, employing also other learned men trained in ecclesiastical scholarship and having searched for, and diligently examined, old Missals and other books bearing upon the subject, have endeavored to restore the Roman Missal to its original purity and to confirm and attest the painstaking care and diligence of Pius V and of those appointed by him. It happened, however, that in the carrying out of this task, as a result of an accurate comparison of ancient books, some things have been improved upon and, concerning the rules and rubrics, some points have been more fully and clearly stated. These improvements, however, flowing as it were from the same sources and principles, seem rather to represent and complete the meaning of the rules and rubrics than to introduce anything new.

"We have ordered, therefore, that the Missal which the same Pius V had edited, thus revised, be printed as faultlessly as possible at Our Vatican printing press and that it be published for the common benefit."

Again, the only reason he did anything at all to the Missal was because through the years the missal had many errors due to printing or whatever. He did not invent a new rite or change the old rite. Your above quote even states: "These improvements, however, flowing as it were from the same sources and principles, seem rather to represent and complete the meaning of the rules and rubrics than to introduce anything new."

The idea that the language used for Quo Primum is merely the theatrical norm used in those days and on that account QP does not mean what it says, is 100% Novus Ordo approved thinking.
The idea that a pope can change, or even totally discard the liturgy of the Roman Rite because popes cannot bind popes, is also 100% Novus Ordo approved thinking.

It is NO approved thinking because that is the NO thinking the modernist enemies of the Church managed to convince so many of the faithful of when this crisis was in it's infancy. It went something like this:
"Why the changes?"
"Because he's the pope, popes cannot bind other popes," and "The pope can do whatever he wants." - This is the approved NO thinking I am talking about. Understand that that answer settled the matter for multitudes of otherwise formerly faithful Catholics who went NO because the pope cannot be bound by his predecessors. This means PPVI had all the authority he needed to do what he did and everyone had to obey.

Further, re: the docuмents of V2 - the same trads who claim QP does not mean what it says, roundly condemn V2 for meaning what they say.  Why?