Almost like a memorized prayer, there are certain defensive gun myths that people will recite reflexively. Some of them are correct, some are true with caveats, and others are just garbage with no basis in fact.
One of the big ones that’s mostly correct is that defensive shootings happen in “three rounds, three seconds, three feet” (or some variation of this, like “two rounds, two seconds, two feet”).
This idea has led to a whole industry of guns optimized for concealed carry.