Good list, and indeed not really advice for beginners.

I'm not sure reading the standard library for language X is necessarily a good way to learn the conventions and practices of a language. Typically a standard library contains a lot of complex corner cases that don't need to be worried about when writing ordinary code.

(Expanding). The standard library authors don't know the users of the code. While when you're writing a piece of code with a limited number of developers (could even be thousands) you might, for example, say "all our accessors for class X return const results" while the standard library authors have to handle the non-const case"