I did not say you won't gain anything from jumping. On the contrary, you must never neglect the actual jumping when you are training for... jumping, that is self-explanatory.
I also did not doubt that if he had not jumped that much he would be jumping lower.
Kilganon is not just another dude that got to add 5-10'' to his jumps, he is arguably the best dunker on the planet and his maximum RVJ is a world class +50''.
Many young kids will look up to him. That is why the advice "just dunk a lot every day" annoys me, it is misleading.
I do believe your n=1 experience that got you to 33'' by just jumping. But that does not change the jump-training science basic facts:
YES, if you jump a lot you will improve your vert some.
YES, people that are naturally strong can go a longer way by just jumping.
But, sooner or later, you will have to strength-train if you want to approach your potential.
Even Kilganon, if a professional coach took him, be sure he would have him strength-train too. He does not have to because he is already over 50'' so why bother. But if he had to chase his full potential and do it right, be sure the squat rack would become his good friend too.