Joint custody says, "When I have it for this period of time I do, say, and act however I want." This is far different from it being "ours". When it is "ours" we make decisions to do, say, and act in the best interest of it so that everyone wins.
We're in trouble when team members start to claim anyone piece as "this is mine" or when a leader has a vision but does not involve the team. Leaders see the danger in team members filing for joint custody.