Honestly, I cannot find any audibility claim on
https://chordelectronics.co.uk/product/quartet . It's a typical BS towards technically-clueless audiophiles, but no direct claim to audiblity, as far as I can see on the Description and Features tab.
IMO there are other devices which are total snake oil, but this one seems like a real technology to me. IMO the effect is inaudible, but precise digital measurements would likely show a bit of difference compared to filters in DAC chips.
It's a pitty the well-known resampler performance database
https://src.infinitewave.ca/ does not include these hardware I/O resamplers, even though it would be perfectly possible technically.