A five percent drop left in the Smart Case over 10 hours.
I defintely think its a bug, as the battery amount dropped, is not consistant over the same period of time.
I might wait a few weeks and reorder another pair and see if that pair is any different. Never know, by the time it takes to receive them, Apple may have a firmware update pushed out to fix this battery drain issue.
Everything else about the Max, I absolutely love.