Or in other words, they were written so as to agree with previously published information.One of the GT developments around Nobles has also been changed by Marc since it was written. Unfortunately, Behind the Claw and MGT Spinward Marches were written with that previous assumption in place.
They never really did, though. At least, I can't recall any mention of low-population worlds with their own barons. The closest is Lewis, but the Baron of Lewis is also the Marquis of Aramis (or the other way around, probably). Also, the Marquis owns Lewis in its entirety (or did at the time he was made baron).The noble you'll find present on and assigned to every member world is now the Knight, not the Baron as previously written. There are still a lot of Barons "of", but now backwaters with 60 people and a sinus problem no longer rate a Baron of their own.
IMTU only member worlds rate a high noble and few low-population worlds are members; most are outposts of members (Lewis is one of the exceptions; it is a member world due to political shenanigans1). Even then, its quite usual for high nobles to double up on titles. Like Yori, which certainly (IMO) rates a marquis but is only a barony and shares a high noble with Regina.
1 You know, it only this minute struck me that at least some of those odd low-population member worlds can be explained by Imperial nobles pushing for member worlds (with high noble titles for themselves) of their own. The membership is purely formal and so is the allegedly independent governments.
Hans