The current behaviour allows you to uncover mutual friends between person A that has all connections hidden, and another person B that does not.

There's no way that I could know which specific friends of person B are also on the friendslist of person A just by looking at person Bs friendslist.

I also tested that "hack" with one of my friends that has all connections hidden. (I only see 1 mutual friend and no other friends)

The result was that I could see 38 mutual friends between him a the mutual friend I have with him.

And yes, that's what I meant. English is not my native language.