I could imagine that steganography is only one part of the puzzle who is the impostor.

Perhaps Apple has a secret departement dedicated to identify leakers. If they found someone they strongly suspect they lay out a trap, for example by only sending him confidential information.

And, if someone innocuously forwards a memo, they have the electronic paper trail of that.

Spionage, counter-spionage and counter-counter-spionage. Apple is waging a war.