Yield comes with experience, I see people come in the store, and say they can't pull more than 2 ounces; No matter the pot size. 2 months later, after a little experimenting, they're pulling more, and as time goes on they'll keep pulling even more.
The argument between genes, and environment goes on; But I believe, it's the combo of both. Even on "bad" runs, where the plants have been locked out, I've still pulled great. I don't believe it was the genetics either, it was relatively speaking low-yielding strains, like sour dub. I think at least a stable environment enables the plant to be more productive in the uptake of nutrients, due to the stability of it's environment. Also since it's dialed, when it is, I think the plant never has to deal with any type of environmental stresses, which could also delay production, and quality.