Couple thoughts after thinking about it a bit more:

• This smells a bit like a quieter way to just raise the price of boosters. Drafts will cost more now, which sucks. They say "Because that is six more boosters than Set Booster displays have right now, be aware the price of a Play Booster display box will be higher than that of a Set Booster display box." Most likely this coincides with a per-booster price increase too which probably (partly) drove this.

• Impact on draft seems way higher than they're leading on, even though they address this. An average of 3 cards from the List per draft has to increase variance. Granted it's now 50 cards instead of 300 in the List, and there is thought to tie it into the set, but that's still more variance. Relatedly, possibly opening 4 (!) rares but 3 fewer commons also has to change the game quite a bit too. 2-rare packs seem not crazy at least, and 3 fewer commons is substantial.

• I'm glad we're going back to just 1 type of booster pack though, I didn't like 2 different packs.

• I hope all cards from the List now make it to Arena! Could be a cool way to get more reprints there.