[caf]

In the recent ruling case (Amalia/Wildgrowth Walker), neither decision (mill cards or leave the same card on top of the deck) ends the loop, though. The loop will still continue with an empty library. The idea is that making the mill choice might eventually tempt the opponent to end the loop, if they have the ability - so that does seem a lot different to the "you must choose to stop looping if you can" case.