`alloc::System` docs contradict "the default global allocator is unspecified"

[QuineDot]

Location

https://doc.rust-lang.org/std/alloc/struct.System.html

https://doc.rust-lang.org/std/alloc/index.html

Summary

System says:

This type implements the GlobalAlloc trait and Rust programs by default work as if they had this definition:

use std::alloc::System;

#[global_allocator]
static A: System = System;

fn main() {
    let a = Box::new(4); // Allocates from the system allocator.
    println!("{a}");
}

But std::alloc says

Currently the default global allocator is unspecified. Libraries, however, like cdylibs and staticlibs are guaranteed to use the System by default.

(And the example was not library-specific.)