I do not see the really problem about this. Why should it be a problem to give personal details, if there is nothing to hide? For sure they will not share any information with others.
LOL.
When you give away a data, you can rest assured this will be used against you, sooner or later.
It's not if, it's when.
And even if you trust the counterpart you give ypour data to, they can lose the property of your data, trough hacking, government actions or even corporate acquisitions.
Crazy that he didn't see any problem or risk about providing his personal details. Since even if he didn't do anything wrong the people who use his data could make up something that can put them in big trouble.
That's the reason even if we didn't do anything wrong we must protect our data and don't just send it anywhere. Its because maybe for now he didn't get any problem but there's huge risk that he might get compromise in future and to bad for them if he didn't know how to solve any serious problems that he might encounter online.
Maybe he could learn something from here
https://www.mavericksafe.com/the-risks-of-sharing-too-much-personal-information-online/ if there's a case of data leaking happened.