After playing the game in OSX for a few minutes, new areas that are tagged for digging don't show the orange shovel highlight. The dupes will still dig the areas, but there's no longer a way for a player to tell what's still tagged for digging. It looks like a graphical glitch.
I've attached a screenshot showing an area I tagged for digging. You can see the "colony lacks hard digging" icons but the whole surrounding area is marked for digging.
Play the game for a few minutes, and tag several areas for digging.
After a period of time, the digging highlights will stop showing.
My MacBook Pro Specs:
MacBook Pro (13-inch, M1, 2020)
M1 Chip, 16GB Memory, Running Monterey Release Candidate (12.0.1 (21A558))