Surely milling yourself is more risky in their deck because if you accidentally mill the 1 plains that shuts off all their fixing for white (Amulet, Wilds and “moose”), meaning GtTF and the Ironwrite are dead cards, plus you loose flashback on Prep. Sure in Mach 3 we saw an opposing Prep and Geistflame, but I think it’s better to accidentally mill one into your opponents yard than mill the plains then draw both your white cards…

What you are suggesting is drafting without any color bias irregardless of all previous picks. While this might work quite well because of the signals of your neighbors, it funnily fails to work if everybody at the table does the same, resulting in completely random decks colorwise. It would be interesting to analyze how much of a color bias you expect at a table and how you should adapt. My hypothesis would be that even a very minor color bias (much less than in reality) would lead to quite orderly results.