That is not an infallible papal or magisterial proclamation. It is simply a “current” position of Rome. Subject to change. Simply man’s opinion
[It must not] be thought that what is expounded in Encyclical Letters does not of itself demand consent, since in writing such Letters the Popes do not exercise the supreme power of their Teaching Authority. For these matters are taught with the ordinary teaching authority [The Ordinary Magisterium], of which it is true to say: ‘He who hears you, hears me’; [Luke 10:16] and generally what is expounded and inculcated in Encyclical Letters already for other reasons appertains to Catholic doctrine. But if the Supreme Pontiffs in their official documents purposely pass judgment on a matter up to that time under dispute, it is obvious that that matter, according to the mind and will of the Pontiffs, cannot be any longer considered a question open to discussion…