The first problem is that you are taking that quote out of context.
His mentality is that if you make 4:20 the standard of fast, your team will have a couple 4:20 guys at the top. If 4:20 isn’t something to be proud of, your athletes will strive to do better than that.
If you go into college and train to run a sub 4:10 mile, you may run a sub 4:10 or come close, but you will not run 3:5x. If you go into college with the intent to run sub 4:00, you may do that or run close. (Dependent on talent of course).
I’m a big believer that a lot of potential sub 4:00 milers run 4:20-30 in high school because that was good enough to win meets and be the best on the team, and they are already doing more than the rest of the team despite only doing 30-40 mpw.