It's been my experience while flying that WN is generally more willing to hold a flight for a few minutes than either United or American. It does seem to be acceptable in their culture - even in cases where the late passenger(s) doesn't have an unusual circumstance.

I misconnected on UA at Denver by less than one minute in a year when I was 1K. Two other 1K's were also running through the airport trying to make it too. One of them asked the GA "You closed the door when you knew at least three 1K's were on the ground, plus possibly others back in coach who aren't here yet, running to make this flight?" Answer: "There was nothing I could do - I get in trouble if I hold the flight."

Although I've never seen the scientific data about "close misconnects", I believe that a WN agent would have handled that situation differently and everyone from my inbound flight, regardless of status, would have made the connection.