Boiling urine does NOT remove the waste products contained therein. It simply concentrates them! (Or if you boil it long enough for all the water to go off, you'll be left with a solid containing urea, creatinine etc. So for sure these people are eating urea, a human waste product which is removed by the kidney.
Since the disease gout is often associated with elevated levels of circulating uric acid, I wonder if these people will be more likely to get that disease or if a healthy kidney will simply just have extra work to do but handle it just fine. In any case it is most certainly moronic to imbibe waste.