Another very good question:
How can you release drawn geometry (wall plug-in) from being parametric?
Is there a global setting to deactivate or is exploding the only way to achieve this?
Exploding the main wall group is one way to do it, then group it back together if you wish.
If you do this you essentially eliminate the attribute library of the wall group so this action is irreversible once you save the file and exit the model.
Another method is to rename the Instance Name of the group (remove the RECT_WALL_ASSEMBLY keyword string). If you do this the plugin will not recognize the wall panel group as one of its own and will essentially ignore its existance.
The good thing about this method is that if you at some time in the future do want to restore parametric ability to this wall panel you can do so by renaming the Instance Name to include the keyword string above.
Just make sure the trailing digits or text after the keyword is unique to that wall panel, so that the plugin does not somehow confuse it with another wall panel.