He is probably refering to total beginners, at least I hope so.
There are two lines of thought to teaching golf. One is to get the fundamentals down before adding any power. The other, swing with normal power so you can get the fundamentals down at the speed at which you will be playing.
I lean toward the second unless one is swinging totally out of control. Learn & practice as one will be playing. Why learn or practice what one may never use in actual play.
Just my $0.02
Rick
We have a well accomplished player here in New Orleans who teaches to practice shooting shots PRIMARILY at warp speed. (This is not for shape of course).
I confess that I practice the same thing on occasion but for the most part I practice shooting shots at all speeds.