Yet in a previous page you stated that you can't expect a 6 minute miler to get to 4:30 or be part of a relay.
Huh? With, or without Stava, it’s unlikely a 6:00 minute miler will improve to 4:30 and be good enough to run in a relay. He would have to leapfrog several teammates to do so. Knowing precisely how faster teammates are training won’t make any difference. I had a teammate that topped out at about 65 seconds for 400m, and he never ran in a track relay in HS.
So have I as a coach but I've also had the former and watch as my son and his friends through proper training improve tremendously. The kid who tops out at 65 in the 400 can be a 5:10 miler and sub 19 minute XC runner which would be competitive in very weak meets like the ones my son's team compete.