Well at least he didn't tell you to do it to "spread the pain."
More relevant here, a good shooter does not always equal a good firearms instructor.
One factor is what @AsianJedi calls the "Magic Johnson" effect. MJ was a great player but he was so naturally talented he never had to work out how to do things in detail, he just did them and thus lacked the frame of reference to coach others through the details of improving their performance. Same applies to some "natural shooters."
Another is many LE/MIL FI's lack depth and/or breadth of knowledge. They are the product of small closed systems i.e. big fish in small ponds.
A third factor is telephone. FI's regurgitating incomplete info or concepts they don't fully understand. i.e. if you can't summarize or explain it simply you don't fully understand it. This results in stories like "be careful with range habits because a Drummer Boy fighting the Germans in Vietnam was killed reloading his revolver because he wasted time putting brass in his pockets because that's what he did on the range M'kay ?"