Be default, the cut patterns for walls, etc. that belong to a previous phase are not shown. The cut lines are also greyed out like this:
The options to tweak this is here: Settings menu > Phases > Graphic overrides. Here is the default setting:
However, if you want to show the walls with cut patterns like this:
You need to tweak 2 settings in the Graphics Overrides.
1. Select the "Existing" row under "phase status", and then click on "override" under 'cut patterns' and and then click "clear overrides"
2. Select the "Existing" row under "phase status", and under 'material', select "Phase Exist" and delete it. (don't select a different material).
The Graphics override dialog should look like this: