What the encyclical is condemning is what many falsely asserted was in the writings of the previous popes – and then claiming these false statements were infallible because they were written by popes! It calls “pestiferous” their citing of the teaching of papal infallibility to try and push through their view of poverty for the religious order.
You’re not making any sense at all. I’ve read Brian Tierney and also Klaus Schatz’s rebuttal (in Papal Primacy) of Tierney’s work, and I’ve never seen anything remotely along the lines you seem to be talking about. Do you have a reference to a Catholic theologian for your above claim?
In any event, the bulls seem quite straightforward, if tedious. Ad conditorem canonum starts out with:
There is no doubt that it is the business of the maker of the canons to take action when he sees that statutes issued by himself or by his predecessors harm rather than help, before they can do further harm.
The “maker of the canons” is the pope himself, and John XII is saying that he is not at all bound by his prior decisions, nor the decisions of his predecessors.
Quia quorundam attacks the concept of papal infallibility on doctrine and dogma (“key of knowledge”) about faith and morals:
However, it is evidently clear from the following that the premiss of the above argument–namely, that those things which through the key of knowledge the supreme pontiffs have once defined in faith and morals it is not lawful for a successor to call again into doubt, or affirm the contrary, though it is otherwise (they say) with things ordained by supreme pontiffs through the key of power–is entirely contrary to truth.
John XII then goes on to deny Olivi’s division of papal decisions into discipline (“key of power”) versus doctrine and dogma (“key of knowledge”):
First, indeed, according to those who hold that the spiritual key is by no means knowledge, but the power to bind and loose, it is clear that the before mentioned assertors, in stating that it is knowledge, have erred. The definition the learned give of the key supports them *: “The key is a special power of binding and loosing, by which the ecclesiastical judge should admit the worthy, and exclude the unworthy from the Kingdom”.
John XII also points out that when popes receive their orders, they do not generally receive some supernatural infusion of knowledge, just the power to bind and loose:
Again, because the keys of which we speak are given in the conferring of the priestly order; but it is certain that knowledge is generally not conferred on one ordained to the priesthood: therefore, according to them, it seems that knowledge is not a key, but only the power to bind and loose should be called a key.*