Well, they certainly broke the 1st commandment of safe travel mentioned in that book.
"Thou shalt go one at a time - and leave someone in a safe spot to do the rescue."
There's no question of "if" mistakes were made, it's just about finding out the details to find out WHAT mistakes were made so that others can learn from them. If someone triggers an avalanche and gets caught, then mistakes were made. The goal is to not get caught in an avalanche. After you're caught, then it's up to luck and your buddies to save you. When your buddies are also caught, then it's completely up to luck. I don't like relying on luck.