Hi Graham,
I didn't succeed to reproduce the problem on the geometry created using offset wall from extruded surface. The "Add bends on sharp edges" is defined by default. The DEV.L is available on those bends now and it is editable. However when I edit any of those DEV.L, the "Return to Driven" option is always available in the drop down list.
Could you please attach the model or clarify more about how to get to the problem you described?
I've checked it on Creo 2.0 M70.
Regards,
Yuri.