Solved
PetterssonAnswer
15-Moonstone
August 22, 2023
You need to check the "Reapply Mirror" button.
EDIT: Sorry, misunderstood your question. Didn't see the second screen grab. I think the answer is that mirroring in Sheetmetal is a recent addition. It used to not be possible at all. As such, perhaps all the functionality isn't implemented. So unfortunately I think there's nothing to do about it, unless you want to get creative with workarounds (copy the driving surfaces, mirror the quilt, use the Offset command to create geometry from it).

