Furthermore, the conventions for the first (parenthetical) use case, as far as I understand, are either em-dash without spaces (Anglosphere convention), or en-dash with adjoining spaces (Continental convention: German, French, etc.), but rarely em-dash with spaces (as in the article).
A spaced en-dash is also commonly used in British english for the parenthesis equivalent. So it's not really "anglosphere".
While there's no central authority, both Oxford and Cambridge University press style guidelines recommend that.
> em-dash with spaces
my favourite (and I hope LLMs never converge to use it)