I don't think that locking the door to some interior room and calling 911 is a good strategy per se. It may
be good tactics, depending on the layout of the home - but it shouldn't be touted as some default thing to do.
I cannot imagine any reason for anyone in his right mind to shoot through a closed door. First, there is always the risk, however small, of shooting someone that someone does no want to shoot. Second, it is awfully hard to shoot to center mass when the target is completely hidden behind, or is only partially behind, a door.
^ I think you've hit on why "lock the door - call 911" may be bad de facto tactic. It can be the equivilant of putting blindfolds on. You've basically given the assailant(s) concealment and the ability to get within 10 to 15 feet of you.
On the other hand, if they pop the door and enter, you've created a choke point and you have the advantage of knowing where the attack is coming from while the in truder has the disadvantage of not knowing initially where he's going to be taking fire from.
But haves you chosen the
best posible defensive position?
If there is a better choke point or defensive position in your home, why eschew a superior defensive position and adopt an inferior one based on a knee-jerk philosophy of "lock the door - dial 911