At one place where I worked, "Fred" was deemed to be the "expert" on one job. He was not a secretive type, rather, he was always helpful. So in my youthful enthusiasm I got involved with helping him. His explanation of what he was doing was not at all convincing. In a word he was winging it, but eventually came up with an acceptable result. His being the "expert" was just a title to allow him to do the job, which every no one else wanted to get involved with.
So secrecy might be just a cover for people who don't really understand what is going on. As in "I can't tell you that" (because I don't know).
Frank