The Vatican has miles of book shelves that contain numerous stories of paranormal encounters, many of which include UFOs. Why the secrecy?
Diana Walsh Pasulka, in her book American Cosmic, spends time explaining that the UFO phenomena is well known to the Catholic Church. If you have read my Introduction and Background stories, you know that my own experience involves an experience similar to what is recorded about the famous magi in the book of Matthew who followed a "star" that "moved" in the sky to wher Jesus was born. Consider stories like this one or of Father William Gill Sighting, with 26 witnesses. Clearly paranormal phenomena involving flying objects, with humanoid creatures, has been happening for a long time and to people of all types of religious backgrounds. It does not seem to be localized to a particular creed or set of doctrines - even within the Christian faith.
The Vatican archives, which are miles upon miles of shelves of books, contain both ancient and modern stories of Catholic experiences of the paranormal - including UFO-style stories. But they are off-limits to the general public. The Catholic church famously lost its battle against Protestantism in large part due to a desire to only allow elites to access information, like the text of the Bible itself. It appears that the Vatican Archives continue this tradition.