Entirely untrue. Unusual is a subjective term. I think it is unusual that people would get locked up in a cell with no human contact save for an hour a day. How is that supposed to punish anyone - making them sit and ruminate with their thoughts? They still do it though. It comes down to a court decision and I am sure if I looked I could find many decisions and precedents set on cruel and unusual punishment.
Arbitrary -
If a judge can easily prove that there is lesson, moral, or character reform meant to be taught through the punishment then it clearly isn't arbitrarily given. It all comes down to the wording a lot of times.
The important part of the article you quoted would be this (the actual test):