That's not true at all. Trust isn't blind faith. Their choice of algorithm, and other factors they can disclose tells a lot about their understanding.

"One reason for them not sharing the details could be that they want the potential hackers to keep guessing rather than making their life easier (No encrytion is foolproof)"

This is security by obscurity, an example of a poor choice. Overall, your statement says more about your lack of understanding of software security than anything else; as their statements can about theirs.