Actually Pete, you may have missed a little nuance to Bob Katz’ comments.
I have done the listening tests, and, under identical jitter conditions, recordings that have been upsampled via a good-quality synchronous converter sound about “two points” better, with a wider, more stable soundstage and imaging.
Of course, some people may prefer the sound of the asynchronous converter on some recordings, because the vagueness of imaging is aesthetically pleasing (shades of vinyl?). Professionals who upsample will generally avoid asynchronous converters because we want to get those last two points of sonic performance.
So, he was actually comparing the sonic results of a synchronous converter to an asynchronous one, not to no upsampling. He wasn’t against upsampling per se, just ASRCs.
Which begs the question, exactly how does dCS’ Upsampling interpolation work? I don’t think I’ve ever seen any technical explanation 
In a quick scan of all the Upsampler manuals, only the Purcell Manual has this to say;
This is achieved using extremely powerful and accurate digital interpolation filters, which introduce negligible levels of distortion.
No other manual even mentions the word interpolation 