I wanted to ask why it's bad, what did you change?

Btw. the example function get_default is badly chosen, because unwrap_or_default exists.

The example even used unwrap_or_else where they should use unwrap_or. Then it uses std::i64::MIN as fallback value where they could use something like 0 that would be a better example and honestly make more sense there.

let parsed_numbers = ["1", "not a number", "3"]
    .iter()
    .map(|n| n.parse().unwrap_or(0))
    .collect();

// prints "[1, 0, 3]"
println!("{:?}", parsed_numbers);

Even without trimming this to something less convoluted, the same functionality (with different fallback value) could be written in more readable form.

Obviously in the context of the page something like this would make way more sense:

maybe_number.unwrap_or(0)

Or perhaps more idiomatic version of the above:

maybe_number.unwrap_or_default()