I like Diaku's insight as to the compression/tension function of the member. It makes sense to me that a Princepost paired with a Kingpost is acting in tension, supporting the tiebeam from the rafter rather than in compression supporting rafter from the tiebeam. In this way it is a sort of "Mini-Kingpost" when paired with struts.
The Queenpost still is vague as to definition although the definition for Princesses post would place it in compression mode. This would make logical sense and clearly define queen post from kingpost on a functionality basis.
I guess it also makes a difference whether it is a true "truss" configuration vs. merely a bent. Unless I am mistaken bending is not allowed by truss definition, all member must be in either compression or tension. We know this is only theoretical as "sag" can be seen an many historical truss examples. So both Mark and Don P. are right? Over time the compression load of a queenpost truss could cause bending in the lower chord (tiebeam) if severe enough this would result in thrust at the wall plates?
Quuenpost = compression
Kingpost = tension
Queenpost weight is born primarily by bottom chord (tie-beam)
Kingpost weight is born primarily by top chords (rafters)
prince and princess replicate parent of same sex? Is this good logic?
