Either way the problem is the reinforcing- core drills will zip through the concrete but don't like steel. Hilti mention the DD350 being capable of coring through rebar, but ordinary rebar reinforcement is a long way off what's used in strong room walls.

Spiral Mattress is incredibly thick and interlocking, and deflector reinforcements like Tangbar and Tordbar are designed to present the maximum angular surface for deflection while also being unpredictable. So when you hit it, even from multiple holes in different places it's very difficult to piece together a plan of the shapes and predict where it is. You can't avoid it basically, it's dispersed right through the concrete and 2 meter walls would normally have Tangbar and the Spiral meshes throughout it.