What makes his library “standard”?
I think the author pretty clearly means "standard" in the sense of "providing functionality at the same level as the C++ standard library".
For example, if I were to say "I'm going to write my own Dune", you'd probably understand that to mean my own broadly-interpreted sci-fi epic, and not literally a clone of Dune with Paul Atreides, the Bene Gesserit, etc.