I think Bill Drills, Blake's Drills, etc are super useful in developing hard skills in a training context. They help in building a consistent, sustainable grip, vision issues with transitions and 'sight picture', etc. They are not, and shouldn't be taught to cops, as engagement strategies. This is where I differ with a couple of trainers I highly respect. Yes.....Bill Drilling a bad guy is likely to be "Highly effective". It also might end up as unlawful force.
I've also trained with Proctor. I still think a lot of the confusion occurs in how some students take in the information. You can clearly articulate that a Bill Drill is an exercise to develop a good grip on the pistol for if you HAVE to fire multiple shots, but some students will go back to the station and say "They're teaching us to shoot the bad guy 6 times as fast as you can!" That has to really be guarded against.....and some shooters just aren't mature enough to have a gun, frankly. And by shooters....I mean cops.