Ambiguous macro call

The guide says right here:

Error: some fatal error has occurred in the parser. For example, this happens if there are more than one pattern match, since that indicates the macro is ambiguous.

This seems not to be the case.

macro_rules! times {
    (a b) => (5000);
    ($x:ident b) => ($x * $x);
    ($x:ident $y:ident) => ($x * $y);
}

fn main() {
    dbg!(times!(a b));
}

Output: 5000

https://play.rust-lang.org/?version=nightly&mode=debug&edition=2018&gist=bf361f3a9a5ab6fd4d4d30b6d9ae2365

Rust just chooses the first pattern that matches. In fact, you can use the exact same pattern twice and the Rust compiler won't complain.

macro_rules! times {
    (a b) => (5000);
    (a b) => (10000);
}

fn main() {
    dbg!(times!(a b));
}

Output: 5000

Am I misunderstanding the description or is the description wrong?

Open src/macro-expansion.md at the linked passage and compare its claim about ambiguous macro patterns with the Rust examples in the issue. Check the relevant macro-matching behavior before revising the explanation. Done means the guide accurately describes which matching patterns are accepted and how Rust selects among them.