Of course they do, your so narrow minded though that you assume distortion is purely harmonics. Measure your inroom performance and tell me is it 0dB deviation across its entire passband? Is it the same for phase variance? Is the step response a perfect peak with no swing back and decay? Will it pass a perfect square wave? When you attach an accelorometer to the cabinet does it have zero resonance? And the list goes on...

All those things are indicators of performance and many are audible, any deviation is distortion. I think that your idea of distortion is one of a gross nature or your just fooling yourself.

A performance in a room follows the exact acoustical nature of that venue perfectly. A loudspeaker deviates from both the source and also the venue - distortion on two fronts. We can only try to get as close to the source as possible and then rely on the source to be as close to the original venue as possible.

FFS bub, ignorance is bliss but your bordering on neanderthal.