Neither WHO nor Tyson claimed that pure water dissolves metal. That claim came from an article you linked about a Japanese science project, which uses a large tank of pure water as part of a neutrino detector. The entire article was a B-story to that neutrino detection project.
Between the author and the translator, the distinction between "dissolve" and "corrode" went missing. Context restores it for anyone who recognizes the conditions present in that tank. That was simple galvanic corrosion, not some mysterious property imbued on water by distillation or reverse osmosis filtration. The exact same process occurs within fresh water and within water in which considerable amounts of electrolytes and minerals are dissolved (salt water).