SET's have a particular sound/distortion.....full stop.2nd order below a couple % has been shown to be inaudible. I think what people who don’t like SETs they have heard are reacting to are the ones with inadequate iron in the output transformer that leads to significant distortion also through the midrange. You can hear this also with a number of PP tube amps as well. You don’t hear it with OTLs or SET where the transformers are not saturated.