Hey, being a resistance member was already bad enough in the empires eyes.
It was a "Boy Who Cried Wolf" Type of thing, If every time the empire captured a resistance member, or heard about some resistance activity, and the members said they were "Arcanian", it means that they would be less likely to notice or investigate reports of the Real Arcanians. This way the Igon and Rain might do somthing, and the empire would hear about "Arcanians in Blauport!", and say "Yeah, and in Salmonville, and in Lockatus, and in Softwind, and in Elwind, and in Schitzotect, buzz off"
And in terms of the cheapening memory, Originally it was Out of memory, in a sort of "Everybody who is oppressed by the Empire is Arcanian" type of way (Kind of like "Every Free Citizen is a Citizen of Berlin", although the speaker would rarely state immediately afterwords that they were a pastry).
Yeah sure it would have Cheapened the memory, but that may not have stopped people from doing it. It's a solution that requires no retconning to make sense.