Is that to say that his personal opinions
and his official opinions are inconsistent ??
No, it isn't. The distinction is not between his personal and his official opinions; it's between his opinions, official or not, and Catholic dogma. As the First Vatican Council promulgated, and as Setanta already posted, the operative words are these:
when the Roman Pontiff speaks EX CATHEDRA, that is, when, in the exercise of his office as shepherd and teacher of all Christians, in virtue of his supreme apostolic authority, he defines a doctrine concerning faith or morals to be held by the whole Church, he possesses, by the divine assistance promised to him in blessed Peter, that infallibility which the divine Redeemer willed his Church to enjoy in defining doctrine concerning faith or morals.
What the Vatican spokesperson is pointing out is that in this case, the pope did not speak ex cathedra
to define a doctrine concerning faith or morals.
And that's perfectly typical for papal declarations: This whole infallibility business is a very limited deal. Since the Catholic Church first promulgated the doctrine of papal infallibility, it promulgated only one new church doctrine
through a pope speaking ex cathedra
. In every other statement any pope made in the past 140 years, the pope spoke as an ordinary, fallible CEO.