Good friend Bill Low, CEO of Audioquest Cables, sent me a note answering the question about purity and perfection in audio.
"The answer seems obvious ... Do No Harm ... meaning that the inevitable compromises required by anyone not so small-minded that they think they can make a perfect product, must be chosen such that that they do not harm the very reason we listen to music.
From one perspective, adding a "tube buffer stage" certainly is causing change, but that change, and presumed reduction is information, might also be a compromise which reduces harm caused elsewhere in the mic-to-ear chain more than it reduces the correct information. This might mean filtering what happened upstream, or reducing downstream misbehavior by damping the ingredients which might provoke that misbehavior ... the way a high filter used to be so extremely necessary on a CD input circa 1980's, especially in solid state electronics.
In order to run a long HDMI cable, way past the original intentions of HDMI LLC, the first level of attack is to passively sculpt the signal, actually reduce it, so that the data can be better recognized (of course you know all this stuff). The next level is also to sculpt/reduce the amplitude, but with a finer chisel ... unfortunately the active chips which do this seriously destroy sound quality, but that's not so bad if one is only feeding a projector.
My point is that less can be more."