As to the inner certainty he evidently felt, two questions arise: do you believe Ratzinger, and do you believe the anonymous source? In the case of Ratzginer: yes, sure I do. And the anonymous source? Anonymous sources are by definition impossible to verify: I mentally put a big red parenthesis around anthing alleged by a person who won't give their name, with a footnote that says, "Pending further verification."
I suspect we all do more or less the same thing. Or should, anyhow.
The Church smackdab refuses to promote unverified mystical phenmomena. The most recent was a series of alleged visions at a town in what is now Croatia, starting over 30 years ago. All the bishops of the Diocese of Mostar have ruled the claims groundless, but public interest has persisted, and he place continues to draw millions of pilgrims. The Bishop has nevertheless prohibited "official" pilgrimages, so thse excusions can't be sponsored by parishes or diocese. They obviously can't prohibit individuals and private groups from traveling there: anybody can travel anywhere they want.
However, the priest who, from the first, was the main publicizer of the (ongoing) visionaries, was laicized and ordered not to have anything to do with it anymore. This, despite the fact that, for over 30 years, millions of people -- and by no means all of them Catholic --- have flocked to this village, Medjugorje (Link).
Which effectively illustrates the non-committal or outright skeptical point of view the official Church takes, unless there's a stack of verifiable evidence.
I suppose I could understand this if Ratzinger had simply said, "I felt this was what was best for the Church, I prayed about it, and I felt peace from God on my decision. Now I'm trusting God that He will grant His grace and mercy to those who are affect by my decision."