Yup, this is what I have been theorizing too re. something I see happening in a garden near me.
A befriended bonsai couple near me never allows their trees to grow out. They start pinching from day one. Heavy fertilizer. In a bonsai pot. Full sun. And they get trunk development to the max, where people see trees they bought a few years before as nursery pencils, and now are show-worthy, several inch thick maples.
I think this was 12 years in a pot, from a cutting.