Unless I'm misunderstanding, it sounds like the argument here is that contracts for coaches should be more like contracts for players.
An OC can sign a 4-year contract. But if he's offered a HC job (promotion) after 1 year, he's free to leave and take it.
A backup QB can sign a 4-year contract, but if another team offers them a starting QB job (promotion), he can't just up and leave unless the team trades or cuts him.
So it just sounds like a disagreement with how contracts are set up for coaches, which is a matter of opinion I guess.
If it WERE like that... it would be interesting. You'd either see coaches take only 1-2 year deals so they don't miss out on opportunities, or they'd take longer contracts but demand more money.
I'm personally fine with how it is. Coaches and players alike get shafted by team pretty often, so if a coach can leave for a better opportunity, then so be it.