Ok, I will quibble a little, Serge. I agree that 44k/16 is a more than adequate distribution medium, although I personally would not describe it as "perfectly" adequate.
I also have trouble with "transparent". To me there are degrees of transparency. It is not a binary, true/false description. We may think something is transparent, until we hear something else we consider more transparent, in which case our standards shift. Personally, this has happened to me frequently in audio, usually with slight degrees of greater apparent transparency over the years, but not so much in recent years. The forward pace in audio has definitely slowed, I believe, except for some schiity backsliding, among other alarming mini trends.
As to your tests, I am unclear on their specifics. But, within whatever limits they may have, I accept them as totally credible, as I do you personally. Except, other very experienced recording engineers have done similar comparisons involving RBCD, hirez PCM or DSD vs. mic feeds, and they reach very different conclusions. Some stake their careers at substantial equipment expenditure upgrade levels in preferring recording and distributiion in hirez because they view it as sounding superior. Some of those guys are also very credible to me.
And, I have my own comparisons along with friends, hopefully all of us with discerning ears, of RBCD vs. various types of hirez at different sampling frequencies/formats from the same digital master. You and I do not agree that RBCD cannot be bettered, albeit slightly, but still noticeably and preferably. Note that native analog or RBCD recordings are not likely to reveal much difference for all the reasons cited in this thread about upsampling.
The 2016 Joshua Reiss meta analysis, carefully read, including looking carefully at the individual tests he summarized, can be looked at in various ways, depending on the reader's established viewpoint. To my mind, it demonstrates that some people, particularly those with prior training in what to listen for, can discern a difference with reasonable statistical significance with hirez, though not a preference which was not normally part of the testing. Others, of course, may read it as indicating such a small overall difference so as not to be worthwhile. And, some individual tests, excluding even the infamous, poorly conducted Meyer-Moran, do not show much discrimination of hirez for whatever reason.
https://secure.aes.org/forum/pubs/journal/?ID=591
Hirez is no panacea, and there is no slam dunk case to be made for it. In the slow evolution of audio, it might be a mere blip at substantial expense and inconvenience to many for not much improvement. But, others of us hear the improvement and value it.