It has happened to me and/or people I'm traveling with multiple times that GS PPs occasionally improperly waitlist for PZ rather than PN. And this is reflected in the waitlist order, at least at T-72. 80% of agents will tell you they can't do anything about this and that you need to remove and re-waitlist the PPs, but they CAN, they just don't know how. HUCA. Every time this happened I was able to eventually get an agent that knew how to do it.

One other exception to the rule that PPs waitlist by passenger status rather than PP source status is that if a GS is waitlisted with 1K PPs, the PPs will only be waitlisted for PZ, as if the pax had the lower 1K status. Also seen this happen multiple times, and in this case the passenger was told by every agent that this was the expected behavior, so it might be true. Any GS looking to e.g. give PPs to a 1K and get them back later should be aware of this.