Actually, the fact that you have to cite official registrar docs is exactly the problem. There are 200+ country TLDs, and by now probably thousands of other self-governed TLDs like .name.

For instance, in Serbia, there is a similar scheme to UK: .gov.rs, .co.rs, edu.rs, but also in.rs (for individuals) and top-level .rs. So someone has registered "iz.rs" and offers free subdomains to individuals.

The fact that there is implied hierarchical trust is what the problem is, and keeping track of individual rules for each TLD is prone to errors.

You're absolutely right, when it's Nominet's actions that actually inspire a lack of trust in .co.uk, given they've been a bit of a hot mess since the early 2010's-ish.

;)

(Edit: although I should add that I'm hopeful that things have improved there over the last few years).