I haven't read this yet and I don't anything about the 'secret archives' but as far as I know Jesus never hid any part of His life.
Hmm. And I've always heard those years in Egypt referred to as just that, hidden. ;-)
Think of these like government documents (of any government). Every government has need to classify documents they produce in different categories, including "secret". Most companies keep personnel documents private, etc.
We're not talking Biblical parchments here.
10 And his disciples came and said to him: Why speakest thou to them in parables?
11 Who answered and said to them: Because to you it is given to know the mysteries of the kingdom of heaven: but to them it is not given.
12 For he that hath, to him shall be given, and he shall abound: but he that hath not, from him shall be taken away that also which he hath.
13 Therefore do I speak to them in parables: because seeing they see not, and hearing they hear not, neither do they understand.