"Unique" means "one of a kind". You can't have degrees of "one" but you can have degrees of "kind": it's reasonable to say the only member of a large category is more unique than the only member of a small category. For example, the last piston-engined aeroplane in the world would be more unique than the last Mark IX spitfire that's still got its Overlord paint scheme. (Though they'd be identical if they were in the same universe, I'm talking hypotheticals.)

The impersonation might not need to be good. If they've met Kenobi before, they might be every bit as frightened of him as of the local wildlife.