The example section of the 4.1.2 understanding text seems woefully dated and not helpful. It just has

Examples

Accessible APIs
A Java applet uses the accessibility API defined by the language.

Does it make sense to provide some HTML custom control examples here just that readers get an idea what it looks like?

• a div turned into a button with role="button" and tabindex="0"
• a div turned into a h1 heading with role="heading" and aria-level="1"
  etc.

Or is it better to leave all this to external documentation like APG, MDN, etc.?