If it's not audible, why should they care? specmanship?
For me it's because they claim to be high-fidelity, not high-enough fidelity. See, when i look at my phone or a random USB-C to 3.5mm dongle, I expect poor performance and you don't see me complaining.
On the other hand, when you ask for anywhere from $2500 (like here), or $5000 (for the very similarly performing Marantz AVR-8805), you damn well be able to at least match the performance of IVX' $70 USB dongle that was engineered by one man working alone at home, and beat a
$9 USB-C to 3.5mm dongle with a decent margin!
I get that licensing, firmware development, HDMI switching and DSP and so on costs money, but there is no reason for a pre-processor costing more than an integrated AVR should perform this poorly. Well, no reason outside of not actually caring about how your kit performs anyways, which is why there's so much salt.
I also have to agree with
@digicidal's point about firmware upgrades, especially at the price. That said, with how primitive and fragile the embedded systems AVR's run are, I'm quite a bit more forgiving than most in that respect.