POI doors have undigable mass behind them.

Testing build: AP-397375

Got into a small POI and opened a door. The doorway was blocked by material that could not be dug out that prevents dupes from moving through.

Above: Security door on right is open. The left has not been opened yet.

Below: Automation overlay to show how I opened the doors.  The left door is now open, revealing the blockage.

On the right, the door has been deconstructed.   The "ore" tiles are not able to be dug out, but vanish when you deconstruct the security door.

Special bonus!!!  Here's a Forum bug: "Log Files" drag and drop does not allow log file type.  It also does not allow you to chose the "Player.log" file.

Player.log