I'm inclined to agree. If I'm fixing to a solid wall, I'll drill deep enough to get a solid fixing - and certainly deeper than 2 inches. If the cable was buried 50mm then just plastered over, I'd *still* drill through it before hitting brick with this principle.
Yup. To me, the only real protection would be proper conduit. But best not to go outside the recommended runs. It's almost impossible to find a situation where you'd be *forced* to.