I guess I was thinking that POPDC was a proxy for any type of PRCL lock. Even if we're sideband locked, there is still some signal in POPDC (although it is very small relative to a carrier lock - ~40cts vs. 1,000cts). However, as soon as this question was asked of me, I realized that one of the 2f demodulated signals made more sense.
Since I want the ability to choose between POP110 and POP22, I have put a little 1x3 input matrix before the PRCL lockins in the ASS model. Since POPDC was already there, I included it as an option in the matrix (in case we ever want to do some PRCL ASS after we have some carrier resonating as well).