I might agree to disagree with you on the first part of the talent measure.
100 points on the tables is significant. For context, that translates to a 1.49.3 800m which while I think is a good time for an 18 year old, is a different level of talent to 1.47.6 which I think displayed (or at least used to!) really high potential. I wouldn't bring in their secondary events (the 800m for Hull and 1500/mile for Hoey) as a measure at that age. It's whatever the top end performance is.
I guess I just don't see the logic behind the "jump" theory - especially with Hoey and how there is no grace for him in that age period of 19-23. So if he had run say 1.45.8 at age 20 and then 1.44.7 at age 22, would 1.42.0 at age 25 seem so crazy to you? Because 1.47.6 at 18 would definitely suggest that a healthy progression would have him around those times at ages 20 and 22 and there are a number of really understandable reasons why he didn't do this. Injuries coming out of teenage years, the coaching turmoils, the family involvement etc etc - I guess I just struggle at the lack of grace here in understanding how these things could have created this plateauing of his career for that 4-5 year period.
It needs reminding that Bryce Hoppel ran 1.48.52 at 18, 1.44.25 at age 22 and then 1.41.67 at age 26. So the one difference between him and Hoey is that Hoey is missing the time at 22 right, or else what - now he fine? It's far to harsh to hammer him for not putting it together in his early 20's. And it's not hard to see how that could have happened right? That camp just bounced out the one guy so far in his career that was able to help them put the pieces of the puzzle together after only 18 months which is utter madness - is it surprising that they f-ed up the kids early 20's and managed to stop him progressing the way he should have.
Hulls timeline is much different to this, including a good collegiate career, a gradual rate of improvement at an older age and then boom, acceleration to a level that maybe Hoey may not even achieve (her PR is worth a 1.41.5). I honestly don't know either way. Both could doing "things", both could not be. If I had to pick one to unfairly accuse, I'm picking Hull.
As for your improvement question - Cooper Luktenhaus just went from 1.47.58 to 1.42.27 in one season across the ages of 15 to 16. How does that rank then in the big picture?