@JaWoodle I caught it on Stream earlier today. Link is at timestamp. Sorry for the horrible sound, but you can see where they start taking the dirt out 2 blocks below them.
https://t.co/0pt1FIpDYS
@JaWoodle A quick update for you. Zeds can still dig down, even with the setting turned off. If you are 2-4 blocks below them, they will hit the block below the one they are standing on.