I have to admit that I was a bit stunned that Dr. R. would cite anecdotal evidence to advise something that seemed at odds with the scientific purity of USRPT, which is its uncompromising adherence to biomechanical and energetic specificity. I was beginning to have premonitions of our faith-based opponents throwing it back in our faces. Understand that this came on top of Dr. R's recent revelation that USRPT does not entirely apply to training for the 50s. Things seemed to be unraveling.
Then I stepped back and took a look at the context, and you are right. He is basically saying that 200 pace is good enough for "government work," so to speak, which is to say good enough for age group swimming, where we simply do not have the time to perform three sets per week of each event that the age-grouper is going to swim.
Perhaps USRP does work for 50s for age groupers, but not for what it does, rather for what it doesn't. It reduces glycogen deficiency and reduces overtraining which allows the swimmer to go fast in a 50 even though 50 sets might be in neglected in favor of 100 and 200 usrp sets.