i don't buy a coach would be operating in this speculative way. a coach would be, put in the work and we'll see what rewards you get. a coach would be like your current reward is not future theoretical times but that time you got at the meet last week. i get a coach might need to update training tactics as things progress but that would be to current times and not future ones.
also, i went to the dominant junior high, was 3rd leg on both relays when we won TF team district, and the HS coach didn't know any of us existed yet. much less have a fairly precise book on our time range. i was back in 9th grade PE waiting for soccer season when the HS TF coach plucked me out based on the president's physical fitness 50 yard.
if this is a coach, there is no way you get another 1 year drop like that. that would be WR stuff. so he needs to make smaller goals. a lot of this sort of speculative stuff ends up trying to tell kids they can drop 20-30s in a season. they then come on here frustrated instead of proud for dropping 15s. as a sprinter i never dropped more than about a half second in a season or .3 off a PR. to me moderate goals and rewarding PRs as opposed to setting huge big picture ones makes the process happy and rewarding rather than frustrating.
and be real. we could speculate he could drop 20. but that sort of thing is really about right now and then the summer, the talent he has meets the work he puts in, and whether he works on little things and weaknesses. we could speculate 20s off and he sits on his tookus all summer and that's that. all you can do is finish this season out strong and then see what shows up other side of the summer. if he puts in the work you update the training concept to what arrives. if not, you deal with that person. it's really about what really shows up. so i don't get hypotheticals other than motivation. the more reliable less frustrating motivation is you put in the work and dropped a minute-ish. do it again i can't promise a minute, can't promise anything, but we'll be that much faster next year.