it applies if you are using 00 ..... I don't use 00.... I use # 2's.... and have 6 rounds I can shoot in one, or use the double barrel one (2 I have ready for home defense). I'm sure I won't have to aim "real well".
Trap shooting, I used to shoot around 196-198 out of 200 rounds consistently. But , it's a small rapid moving target.... I'm sure in a SD situation, they won't be moving near that fast and the targets are MUCH BIGGER & much closer. And if I use the double barrel and let both barrels go at the same time, I'm sure it will be effective. The handgun is for anything else that's still moving... and is a threat.
But, if you are 10-20 yrds away and using 00, then you best be aiming really well.