HTML "id"-attributes in specification not unique

[Exlll]

I was trying to create a link for subsection Canonical Form of section 10.2.1.4. For that, I inspected the HTML and copied the value of the nearest id attribute, which is canonical-form. Doing so would normally allow one to create the link https://yaml.org/spec/1.2.2/#canonical-form. Clicking on that link, however, sends you to section 3.2.1.3.

According to the HTML specification, section 3.2.3.1, the value of this attribute should be unique.