Great, so is there actual data (whether DBTs or measurements indicating audibly significant levels of distortion) from actual commercial DACs or CD players that supposedly have "digital glare"?
Good question. Thanks. Made me think of yet another bias.
During one of my recent encounters with "The Glare", I had what I consider to be a good professional desktop DAC (Focusrite Forte), which to me sounded transparent with good professional near-field monitors (several models). I also had a good competition-grade car amp (Helix H400X), which to me sounded transparent with good passive speakers (also several models).
I wanted to find a car amp comparable to H400X in sound quality, yet smaller, fitting geometrical constraints of a particular car. I have both line-level and speaker-level A/B boxes, massive transformer-based 12V bench power supplies, sound level meters, oscilloscope, spectrum analyzers etc. However, I also had very limited time allocated to that stage of the project. So, as soon as sighted A/B testing allowed me to pick one out of four candidate amps, I immediately moved on to the next stage.
During the evaluation, one of the other amps, a well-reviewed in English-speaking press D-class, proved to be glaring to my ears. I just couldn't stand it, leave alone DBT. Interestingly enough, the winner, which I bought new for about 40% of the H400X price, turned out to be indistinguishable from H400X to my ears at carefully matched volume levels. At some point, I actually forgot which one was A and which one was B, and had to trace the wires from A/B box to figure it out. I got good money from selling my H400X on eBay
A salient point is that I didn't bother to measure in depth, figure out, and document why specifically that D-class sounded so harsh to me. I simply got rid of it as soon as I could get around to doing it, and never thought much about it, until now. Neither was I willing to tell anyone what model that was, because, you know, sound perception is so subjective: as far as I could tell, the manufacturer sold tons of them, and other people must have been happy with them.
So, here's your answer: some (most?, almost all?, all?) of those who could measure and publish the glaring gear characteristics don't bother doing it - there is usually neither time nor incentive to publish a negative review, especially if it could be perceived as entirely too subjective.