2 things -- I think if Pono is selling a 16/44, it is the same as the CD, unless the artist has done multiple 16/44 masters (like Zep). Why wouldn't it be? They are not trying to get remastering done at 16/44.
As far as my Let It Bleed, I agree that provenance is not known, and I would appreciate more from the labels and the stores.
If I downsample to 16/44 I would have to dither, and then the test would be skewed with my dither algorithm. I probably have 4-5 I could use, each sounding slightly different.
I can do that test, but I'm more curious about SQ based on what's for sale to consumers. If I can buy the Stones at 16/44 or at 24/88, I'd prefer to test those 2 against each other and not introduce my dither. Chances are they have a better one than I do.
Remember, there's 2 types of 'remasters' -- there's just the digital transfer type, and there's a whole re-mix session resulting in a new master. You would hope that they disclose the latter, but the digital transfer should shoot for accuracy and matching the previous format sonically.