There's a big error in this article. Prophet DOES NOT need to have "has all its uses of "Spread Religion" remaining", he only needs 4.
In other words, if you have Great Mosque of Djenne
https://civilization.fandom.com/wiki/Great_Mosque_of_Djenne_(Civ5)
and the Great Prophet can spread religion 5 times instead of 4, you can use it once, and only then go to build Holy Site. I even tested it in my current game to be sure.