Pretty sure the whole THD cat was out of the bag back in the late 70’s and early 80’s when relatively high THD tube amps crushed relatively low THD solid state amps in terms of sound quality. So, it’s not exactly news. The tube amps in question sported 0.05% THD vs solid state amps with "vanishingly low" THD around 0.001% or whatever. You know the amps I’m talikng about, the ones that’d rip your ears off.