Yes, from what I've seen, it definitely holds true as long as the faction in question is at peace with all its neighboring factions. Once they are at war, I'm not sure what the priority becomes, but I've definitely seen rebel settlements go seemingly unnoticed by factions who were at war with multiple neighbors.
A common example of a faction in M2TW avoiding war with neutral factions in favor of taking rebel settlements is Scotland sending a fleet to capture Antwerp or Bruges once all the British Isles settlements are occupied by them or England. What one would more logically expect is for Scotland to besiege York.
Bookmarks