I do not condone the way the bus driver handled the situation, especially the one who would not let the husband off the bus. However, I must play devil's advocate and present a scenario I have been involved in.
I was on the red route(WL to MK) and the fireworks had recently gone off. It was a hard close, meaning fireworks=park exit at the same time. A guy came down the dock with one or two kids. The kids got on the boat and the guy stayed on the dock and explained to me(I was deckhand on the cruiser) that his wife forgot the camera at the restaurant and "she'll be right back." Being inexperienced at the time, I conferred with the pilot(it is ultimately his call) and he foolishly agreed to wait for the wife. 2 minutes...a mere 2 minutes later, his wife came running and got on the boat without so much as a thank you for waiting for her. That 2 minutes ultimately gave time for the launch(other boat on the route) to catch up to us, ultimately meaning the people at MK were waiting over 20 minutes for a boat because our cycle was thrown off. Additionally, there were low water levels at the time, so west angle was shutdown and the gold, green, and red routes were all sharing the dock at MK. Thus even after we got there, we had to wait for a dock.
Waiting for 2 minutes meant A) the people on the boat were upset that we were waiting and B) there were 120+ very unhappy people on the dock by the time we docked unloaded, and started loading. I took a lot of heat as the deckhand from those people on the dock.
In a slightly less extreme case, I point out the ferry boat cycles. Our rule is keep your party together. If someone is slow, wait for them. Don't send kids or the more physically able people ahead to hold the boat. Why? because when there is a gap, we need to GO, not wait. Waiting for that extra person can mean that 5 other people suddenly catch up, then some huge wave comes(because generally crowds do come in waves) and now we're stuck while the other ferry is already halfway across the lake.
Again, I DO NOT condone the way the bus driver handled the incident. However, I see the bus drivers point of view. When it's time to go, it's time to go. There is a reason, one way or another, for that decision.
A little tip though - the 15 sec thing is usually a way to give time, yet make people hurry, but without running. It's a very delicate balance
edit: thinking back on that first story, I think us waiting on the wife ended up causing us to get caught by lightshow and that's what caused the wait time at the dock to be so long. After that, whenever I've been driving and I know lightshow is going to be in the waterbridge soon, I will tell the deckhand to go even if there are people running down the dock that we could have waited for. It's rare that I have to do it, but I always look at the big picture.