How about asking someone who knows a thing or two about being an early bloomer? Let's see what Richard Gasquet has to say about that.
Interview "souvenirs de jeunesse" avec Richard Gasquet, l'ancien prodige du tennis français.
www.tennislegend.fr
So, two things: you are going back to 30 years ago and earlier. The eras were different. At the time, the players traveled only with their coach. The training has changed, the players are bigger, stronger, a lot of them travel with a fitness trainer... What was possible for Chang at 17 in 1989 might no longer be possible for a player of the same age and same development stage in 2019. Even Gasquet thinks the players have gotten much more stronger between 2005 and the year of the interview, 2016.
I kept the part about Nadal because I found interesting how Gasquet noticed how quickly he seemed to improve in a very short period of time. Also, Nadal was physically very developed for his age, more than Felix.
As for the work to do, I fully agree Felix has still has plenty to do, but he says so himself. He even asked the fans to be patient in an interview not long ago. I don't understand why fans seem so quick to base his future on the present, as if it was not possible to learn how to compete under pressure and improve his shots. Many chronically anxious people are able to learn to deal with it. I studied for a long time, came back for another degree as an adult, and I can tell you that I was still improving my studying techniques and how I was preparing for exams until the end, becoming more and more efficient. A teacher in high school once told us that we were at the peak of our capacity to learn by age 22. Far from true, believe me. Let's wait before worrying too much about "established patterns". He'll learn, and he'll learn how to learn too.
Felix's tachycardia episode showed up right at the moment he went back on the court to start the third set. At that point, the first set went 7-5 for Denis and the second one was won by Felix with the same score. The match could hardly have been more equal. Unless you believe that going ahead 4-1 in the third against an opponent who was almost fainting on the court is meaningful tennis wise.