This scene shows that when Thomas was doing a bet with Carlos Mattis as he surprises him when he easily clears a 6'6''. As the numbers got higher he had eventually cleared a seven foot. Which made that this was a sight of something new. A textual evidence sighting is (Epstein 2) "Without a semblance of graceful high-jump technique - Thomas hardly arched his back and his legs flailed in the air like the streamers tailing a kite and he cleared it". With that made his firsts steps in becoming a championship or competing. This will take him somewhere in life.
As he adapted to what he is doing now, he goes through tons and tons of championships and is placed world wide across the whole town. As well when he develops he overpasses many and now has a career of high jumping. Textual evidence supporting with what I said is (Epstein 5) "Thomas competed at the Commonwealth Games in Australia against some of the best professional jumpers in the world, wearing tennis shoes." This suggests that because of that one et it made Thomas go through a whole lot of adventures, adventures that he probably didn't think he knew was available to him until now.
This suggest that Masaki Ishikawa tells Thomas about his extraordinary gift called Achilles Tendon. Which explains being a all time natural of becoming a high-jumper and passing high ranks of jumping. Textual evidence supporting my reasoning with this including the picture is (Epstein 13) "Ishikawa noted both Thomas's long legs relative to his height and also that he was gifted with a giant's Achilles Tendon." That suggests why it was so easy for him to do high-jumps.