You're almost correct. Sure, new fighter pilot production is maxed-out, but if TX courses were the fix Big Blue would be all over that.
The REAL limfac is the number of fighter cockpits we have. To get a guy "qualified" to do a NON-flying job that requires an 11F, he must first be experienced in his MWS. As we've cut the overall number of fighter cockpits available, AFPC is seeing the second and third order effects of those dwindling cockpits: A smaller pool of "experienced" fighter guys that they can send off to do "other" jobs.
While ramping up TX courses would improve the number of current/qualified fighter pilots, there's no way to increase the number of cockpits. (Well, we COULD buy more fighters, but I have some coastal land in North Dakota I'd like to sell you if you believe THAT will happen soon...)
Increasing TX course throughput just kicks the can down the road a few years anyway. Eventually, those older dudes will "age out" (think: Rainman) and be useless to AFPC. Without keeping the B course numbers high, AFPC would only fix the problem in the near term and create a much bigger problem a couple years down the road. (Ha...AFPC has NEVER done that before, RIGHT?)