Haven't seen this before. Found a flight with "P" availability but it prices as a "Z" (about $480 OW). An earlier flight on the same day does price out as a "P" (about $420 OW). Turns out that the "P" on the earlier flight is an S-up instead of the usual V-up, and the later flight is V9 and S0 and so the "Z" is the cheapest FC fare.

Anyone else seen this?