Not everything has to be proven, right?
whether he should publish the balance received from his salary or give the address to the public, I do not think it is necessary because I believe he is telling the truth. He might be able to share tips to convince someone of Bitcoin and I think teaching the boss won't be easy but I'm sure he has a way of conquering it.
A person who is able to teach his boss about Bitcoin very well is a very extraordinary person. Because he needed to make his boss believe and be interested in Bitcoin, indeed it was not easy to do considering he is an employee and the person he is going to teach is a boss who always pays him a salary.
In this case he just needs to have good communication every day with his boss so that what he wants to teach can be conveyed correctly, because imparting unusual knowledge to a boss clearly requires a different method and time than most people in general. And regarding showing a balance that already has a wallet, I agree with what you said because I don't think it's important to do that because there are still many ways to make someone believe in Bitcoin without having to show the contents of the balance in the wallet.