No, it's nothing you've done wrong. It's the analyzer. Plugins don't see "left" and "right", they see two inputs that may or may not be so designated. When you route a mono signal into a stereo effect, it just sees data on one channel, which this analyzer is displaying as "left". More sophisticated analyzers sense a mono input and alter their displays accordingly, but that doesn't mean this one's lying to you. Waves has traditionally offered mono and stereo versions of their plugins - maybe there's a mono version of this one too?