I'm not sure if I completly understand your question but here I go;
The point of transplanting and not growing in just one medium'ish sized plant from seedling to harvest is, that a big pot will be "too much" for a seedling. It takes more water and it holds onto the water longer. A seedling no way needs that much water and that will harm the roots and the plant.

Hope I answered your question, and that's all info I got from posting/getting answers and reading :jointsmile: