You both have your points but I think
@antiterror13's reasoning is closer to the PLA's own way of doing things.
What you, Andrew, says can basically be compared to the situation in the 1990s for the PLAAF. Did they absolutely focus on boosting the production of J-11s? No. J-7s, J-8s and Q-5s were still massively produced. It's one thing to reach a rather simplistic conclusion from a purely doctrine-centric perspective, but every military has its own momentum, and a variety of other factors equally importantly chip in. That's the reality.
I guess what I'm trying to say is if the PLA can come above all the other factors (economic, habitual, redundancy/risk-related, etc.), yes, maybe they should theoretically focus on getting "a lot more" J-20s as the utmost priority. But it's more complicated than that.