I was wrong with that expectations. Double second cousins are just the children of double first cousins which is not rare at all.
What I meant was triple first cousins or higher levels of first cousins, which happens when e.g. three children of family A marry three children of family B. All of their childrens are triple cousins to each other sharing the same four grandparents. I think sorting double cousins by families could make that very easily recognizable. I’ll try that instead of double second cousins and higher degrees which are just descendant lists of double cousins.