Sure, so what I was driving at with asking Paramandur about their familiarity with Faction War was that there were two specific choices made in the caption labeling for the illustration involving Rhys.
The first was selecting Rhys as the NPC to be portrayed and described. They could have selected any number of Planescape character, including for instance Factol Alisohn Nilesia (who theoretically survived Faction War, by virtue of being sold into slavery on the Lower Planes IIRC). They could have said "Guildmaster Erin Darkflame Montgomery", for example. Instead they opted for the one ruler who was explicitly left alive and active in Sigil.
Then the second choice is using the title Guildmaster, as opposed to any number of other titles: Lord, Ruler, Leader, etc. They could have used no title whatsoever. They chose guildmaster. Which is relevant because in the aftermath portion of Faction War, when the factions were kicked out of Sigil they were replaced by the Sigil Advisory Council – which consisted of various guilds, and Rhys was a member of that group. "Guildmaster" in this context strongly evokes the aftermath chapter of Faction War.
Taken separately, if we had just "Rhys" or if we had "Guildmaster Montgomery", I think your assertion that it's just looking for a term everyone understands, would be more plausible. But together, they form a picture of two deliberate choices, both of which point toward Faction War.