I think Brandt is talking in generalities. Tom Brady obviously took less money for a long time allowing NE to keep their defense stocked and give him some weapons. He left NE frustrated b/c NE stopped getting him weapons with the discount he gave them.
I also disagree that saving cash helps owners. As Brandt himself stated in this piece, owners are already multi-billionaires. They don't need cash. So, that argument holds no water. Owners like Jerry Jones would spend far more than the cap allows, if he could.
The fact is that there is a finite amount of money teams can use to sign players and they are obligated to spend it by the CBA. So, if Dak decided to sign a contract worth 40M a year instead of 50M, that 10M savings doesn't go into the owners pocket. It goes to another player.