Your player needs to understand that it takes years and years and more years to work on their stuff, like you know Rome wasn't built in a day. Thats why guys like David Price and Sonny Gray chose to go to where they did first and came out ready to play the ml game within a season. Others can be ready sooner, but its a long, long hike for most. Projection is important because they look at what you will be like at 23-25 not at 18 (college is different).
Unfortunately there are coaches who want very tall pitchers. I remember a coach telling me once he prefers to look up to his pitchers, that is a preference, and they have reasons why. Work on the stuff, stop worrying high velo at 17,18, find the right program and go for it. That's the secret to doing your homework during recruiting. I mean if all of the pitchers at one program are all over 6FT, there is a reason for it. And that downhill plane does mean something.
I don't remember son ever being impatient as to when "that day" will come. It was about enjoying the moments. This is what we work on this season, this is what we work on next season. I think parents push too much too soon these days.
There is SO much more to it, not all about height and velocity, though that helps. Its also about being right handed or left handed, does he have a beard at 15,16 or a babyface, how the pitcher delivers the ball, his mechanics, run on the ball, inside outside, type of pitches thrown AND movement. I mean if you throw 95 and it comes in as straight as an arrow, no one will care how tall you are.
JMO