Seen it before
Hopefully, if accurate, he wins. Too many managers abuse their position these days. Probably more so back in the days when you couldn't get anything done about it.
In a place I worked where the manager of a different department where that department was linked to the other department was also "mates" with people in HR. This manager would then "gossip" all the confidential info they'd got from their HR mate to another friend that we all knew who blabs about everything.
The amount of breaches via this manager was shocking unfortunately we could never get physical or recorded evidence so couldn't take it further.
It 100% was happening because there were points where this manager would tell their friend something about someone else before that person knew.That person found out and kicked up a minor fuss but it was just brushed under the carpet. Just a shame the person involved in that case couldn't be bothered with the hassle of taking it futher.
A simple subject access request would of also caught this manager out in other instances as we were sure they were stupid enough to be doing some "discussions" over corporate email because they weren't aware of "subject access requests".