Why would a doctor insist on a liver biopsy for someone with elevated urinary copper even though a fibroscan came back normal??

Confirmation, stage: Abnormal blood levels of copper/ceruloplasmin?. Liver biopsy confirms Wilson's disease, extent of damage to liver, help in prognosis, detailing a baseline for effects of treatment. Fibroscan is most accurate at the "extremes" (normal vs cirrhosis), but much less accurate in the middle. Likewise, it may show fibrosis (reversible scarring), but does not give information re: stage of inflammation