Paul Howe of Delta "Blackhawk Down" fame has the actual experiences of being ambushed, taking deadly fire, casualties, being outnumbered, on the run and fighting under totally 'reactive' and changing situations. He knows what's up.
Like Matthew Temkin said:
"One of the reasons why I have sought the advice of combat veterans is...that these men have insights that can only be learned by placing one's butt on the line. Anything else is second rate.
(someone) with zero military/police/security/combat experience should be more humble in the attitude department."
Many trainers have never even been in one gun battle or even been shot at. They teach tactics from hearsay to the less informed and not from real life experience. Case in point: 'stand and deliver', commonly known as stand and 'die', will get one killed needlessly.
Anyone that would opt for 'stand and deliver' - except in the most dire and uncompromising circumstances - is a fool. Period.
A ¼" of muzzle deviation off target moves the POI 12" at 15ft. A moving target is harder to hit. So, move!
Bottom line........It's about surviving. Pay attention. Don't freeze. Whenever possible, always move when under an up-close attack.