I got that "client kingdom" message too. I can not remember well and even though it's weird, I think, that no matter which of the two factions appearing in that message became a protectorate, this message appears. I mean for example carthage takes over numidia as a protectorate, you get this message, but you won't be able to tell from it, who is who. I've had that in a BI campaign. Someone can confirm that?