I know of a warder in a prison. When I asked him how prisoners manage to smuggle things in and out with ease, he said, “Security is only as good as the least paid employee.”
So I agree it has to do with stopping his contacts. Plus safety from other inmates factors into it as well.
According to google, the cell is 7’ x 12’, which is roomy only for someone accustomed to living a New York city studio apartment. All furnishings are concrete - the bed the table, the “chair”. Your toilet is right next to your bed. You may or may not have a TV or radio - they can, after all, take any privilege away. You may or may not be allowed books. Or any other form of diversion.
This isn’t like your bedroom where you get to decorate and arrange things to suit you. This is a cell that doubles as your toilet/bathroom.
Maybe a cell with 20 psychopathic idiots would be worse, but a supermax cell still sounds pretty horrible to me in and of itself.