What constitutes a remake of a documentary? Would you consider Milk to be based on The Times of Harvey Milk? Rob Epstein, who directed the latter, was thanked in the credits of the former and his film was surely an inspiration. His footage was even lifted or recreated for parts of Gus Van Sant's dramatized version. But Milk was ultimately deemed an original work, at least as far as the Academy Awards are concerned.
If you were to argue the case that the biopic is based on the documentary, where then would you draw the line? Is Monster based on Nick Broomfield's first Aileen Wuornos film (he too is thanked)? Is part of Munich based on One Day in September? And speaking of films by Kevin Macdonald, is The Last King of Scotland at all a remake of Barbet Schroeder's General Idi Amin Dada? It does feature footage from the doc, after all.
There's no denying Cate Blanchett's segment of I'm Not There is lifted from D.A. Pennebaker's Don't Look Back, but it's easier to say the latter was merely used as reference. Frederick Wiseman meanwhile insinuates Stanley Kubrick stole much of the first half of Full Metal Jacket from his own boot camp film Basic Training, which was indeed used by Kubrick as uncredited research material. The later fiction film is considered solely based on an autobiographical novel by Gustav Hasford.