Wired reverb plug in behaviour - distortion.

I don't know this particular reverb, but it wouldn't surprise me if the reverb output is boosted a little. It's not that rare. Sometimes users may complain that a 'verb doesn't have enough output, so the makers may boost the signal in response. The issue with a reverb (at least those I know) is that the output is highly-dependent on the content of the input as well as the parameter settings. Sometimes the right combination may cause a surprising jump in level.

I do the best I can to calibrate my presets to unity gain using pink noise as a source. Even so, you're simply not going to get unity gain if--for example--you've got an input that's mainly high-frequency and a 'verb with a big rolloff. Pretty much the nature of the beast.