Please understand that correlations range from very weak to very strong.
So far what little information the company has given on the strength of the correlation between dose and blood concentration indicates that it is not a strong correlation.
Please don't over interpret the word correlation in this case. It's not a strong correlation. I suspect that is the driving force behind the gut microbiome study and the genetics studies. They are trying to understand why the correlation is not stronger so they can address the factors involved. Since blood concentration has been shown to a large factor in positive response to 2-73, figuring out how to achieve that high blood concentration is very important.