A team decides they will poach another teams coach while that team is involved in finals. So out of respect they ring the CEO. So what do they say to the CEO?
"Excuse me, I know you're in the finals and talking to your assistant coach could cause unutterable damage to your finals campaign, but we'd like to discuss employing him as a senior coach next year." And the CEO has basically no choice, he can otherwise say yes, which everyone will know about soon and has to cause some kind of ruction. Or he can say not till finals are over, which will have pretty much the same affect, possibly more as it will be so heavily rumoured both the senior and assistant coaches will be wondering if it's true.
Talk about professionalism all you like but when there is uncertainty in your job it does cause you to think differently. The idea of the handshake agreement is ludicrous, there are 18 teams and most of them will just use any unofficial rule to get a jump on the other teams.