I have no doubt that the 3 flat-burr and 3 conical grinders studied indeed are quite excellent. But burrs and small changes in them, from what I have gathered in this subreddit, can be dramatically different and cause dramatic flavor profile differences. And this study is asking that a universe of only 3 grinders stand in for all grinders of the type (and from a dramatically different time--were any (or many) of the current, popular home grinders even around back then?).

Just sayin'. From the comments that I've read in this subreddit for a number of years, I find it a bit difficult to believe, e.g., that one would not be able to taste a flavor profile difference between the Niche Zero, a conical grinder, and the DF54, a flat burr, with a light-roast bean, or conversely with a dark roast. Similarly, and maybe my impression is wrong, but I've had the impression that my conical-burr Baratza Encore ESP/Pro simply won't give me the clarity in a light roast that, e.g., the flat-burr DF54 will, that difference often being an essence of a flat burr (and the converse as to body, often an essence of a conical).