I was scratching my head over that one, myself, because I do not think of "gold and precious metals" as a "sector."
As far as I'm concerned, the "sectors" are as described in Wikipedia's article on the Global Industry Classification Standard and this document
All of which have had and still have stable Vanguard ETFs.
According to Wikipedia, "gold" and "precious metals" not only are not sectors, they are not even "industry groups" or "industries." They are down at the sub-industry level, of which there are 89.
So the question is "Does Vanguard think one sole fund targeting two out of 89 narrow sub-industries is a good idea?" It's sort of like asking "should Vanguard add a fund targeting brewers, and one targeting commercial printing, and one targeting security and alarm services?