The relevant section of the Vatican II Document Lumen Gentium (excerpted from LG 25): This religious submission of mind and will must be shown in a special way to the authentic magisterium of the Roman Pontiff, even when he is not speaking ex cathedra; that is, it must be shown in such a way that his supreme magisterium is acknowledged with reverence, the judgments made by him are sincerely adhered to, according to his manifest mind and will. His mind and will in the matter may be known either from the character of the documents, from his frequent repetition of the same doctrine, or from his manner of speaking.
Is this a change from Pre-Vatican II or would you consider it as more of a clarification? I personally don't trust anything from VII onwards unless it is a re-iteration of previous doctrine/dogma/documents. Also, it can be difficult to determine when a statement pertains to "faith" because almost anything he says is at least indirectly related to faith.
I would consider it a clarification.
What has changed is the media/access to what the Pope says and does. 25 years ago one would be hard-pressed to find out what the Pope was saying even if it was directly addressed to you (i.e. finding and purchasing encyclicals was challenging). Now if the Pope moves his thoughts can often be found via twitter or a Google search.
The document was written for an earlier situation, and should be understood in that context.