Some info on the word metal as used in astronomy: https://briankoberlein.com/post/hydrogen-helium-metal/ https://briankoberlein.com/post/hydrogen-helium-metal/

Some info on the word metal as used in astronomy: https://briankoberlein.com/post/hydrogen-helium-metal/ https://briankoberlein.com/post/hydrogen-helium-metal/ The short answer is that the fraction of metal is so low, they don't care enough to call it something else.