From experience, the information provided on gov.uk can be incorrect because it is simplified too much. Very important aspects are lost and it becomes misleading.
As the saying goes, simplify as much as possible, but not more.
Although note that there's a non-zero number of professional linguists and grammarians seem to consider Strunk & White to be prescriptivist nonsense that you're better off ignoring.
From experience, the information provided on gov.uk can be incorrect because it is simplified too much. Very important aspects are lost and it becomes misleading.
As the saying goes, simplify as much as possible, but not more.