Interestingly enough, that's usually the European way. I was surprised when Amorim made his dig about being the manager, being the coach is the norm on the continent.I suppose it also depends on what the board want.
Maybe they are looking for a yes man whose only job is to coach the players he is given. Toes the line and knows his place.
Surely the best is a mix, DoF and manager working together but the manager has to have the final say. If either strongly objects, the player doesn't get signed. No point buying a player the manager doesn't rate though