It's called the Tueller drill. The purpose is to prove that the average person who doesn't train can be physically touched befor drawing from a holstered postition And placing an accurate shot on the target because of the stress that's induced from being attacked. Therefore, never allow someone you may suspect of being a threat to ever come any closer than the 7 yards, at a bare minimum. This rule is used to help justify law enforcement involved shootings. The idea is that even if you stop the threat, you've now Increased your chances of death if you were "touched". It's meant to be a very general drill that helps to illustrate the difficulty of high stress firearms engagement from a sudden or unexpected attack. I wouldn't say it's bullshit, but some people teaching it are probably bullshit artists.