I've always understood the PA waitlist is displayed to agents in alphabetical order, but maybe that is really old information?

Interesting that the sponsoree gets on the PA waitlist, but is not adjacent to the sponsor. Maybe the sponsoree is really at the top of the PB waitlist?

It seems like more people are suggesting the PA waitlist clears, when NC/NF inventory becomes available, by status then fare class but what is the final tiebreaker? Date and time added to the PA waitlist? Is that what the OP is seeing when they identify themselves at position #4?