I read on r/MagicArena that, at least based on public information from Wizards, we don't *know* that "You draw two hands, and it selects the hand with the amount of lands closest to the average for your deck."
What we know is closer to: "You draw two hands, and there is some (unknown, but possibly not absolute) bias towards selecting the hand with the amount of lands closest to the average for your deck."
I take it that, if the bias is less than absolute, the consequences for deck-building are in the same direction but less extreme.
This is a link-post for my latest Magic article, posted on Channel-Fireball: Arena’s New Opening Hand Rule Has Huge Implications For How We Play the Game.
Posting here is a more reliable way to engage with me than commenting there, but they have a robust comment section of other Magic players.