Stone covered metal shingles

Have been asked to clean these shingles. They are a steel or tin substrate with a layer of asphalt/stone over top. Homeowner says he has pressure washed himself before (high pressure) and had another company do the same. My question is should I treat them like regular asphalt shingles and low pressure a 2-3% SH mixture?

I would find it easier to not wash them

They only roof I wash now is asphalt. Spray and forget. I definitely would not touch these and I especially would not walk on it because they will crumble under your feet like a soda can.

If you really want to tackle it, the safest route is find out the manufacture, call them and ask how they recommend you clean it.