I'm surely at the back of the line of any folks wishing to criticize them for either where they were or how they responded. From the above article they regrouped well enough to possibly have saved lives. Good for them.
I don't know how you'd "drill" for surprise bear attack and until it happens and "fight or flight" kicks in, how could you really know how you'd react? I guess if I had my spray in hand I might be able to pull it together and use it, otherwise running would seem like a great idea!
For some reason, I thought of this fine military training film, which shows how reluctance can be overcome in the right circumstances. Snakebite! (Bananas)
A company I once worked for was doing remote fieldwork in Alaska. They hired a fulltime armed guard who patrolled the area for bear and scouted new worksites in advance of team moves. He was doing just that in a brushy area and surprised a bear, which mauled him before he could get off a shot (he was carrying a rifle at the ready with safety off). He was heloed out and survived, but we had to rewrite the protocols afterwards.
If it can happen to a "professional" it can happen to anybody.
One of the boys was from my local area. In an interview he mentioned they ran even though they knew they shouldn't. He was not one of the boys who was seriously injured.