Well, it came from the horses mouth. Maybe he was lying, who knows.
Improving max strength is a small cog in a large wheel, that is for certain. Was his increase in the back squat (overrated) the defining factor in running a PR?. Maybe, but personally, I wouldn’t have thought so. Its a big wheel.
Although having said that. I still believe one of the defining factors of Ben Johnsons success over his competitors, was his 600lb squat.
With sprint training, Dr. Fred Hatfield probably couldn’t run for $hit.
I’ve seen some athletes in college & uni increase strength & run slower. A decrease in relative strength?. Probably. I guess strength is important but not at the expense of power.