Note that Details and Summary here are not mere text labels: they’re the actual semantic HTML elements used. Here’s a sample output:
<details class="wp-block-details">
<summary>System Requirements</summary>
<p>
Requires a computer running an operating system. The computer must have some
memory and ideally some kind of long-term storage. An input device as well
as some form of output device is recommended.
</p>
</details>
From the technical specification (MDN):
The <details> HTML element creates a disclosure widget in which information is visible only when the widget is toggled into an “open” state. A summary or label must be provided using the <summary> element.
So changing the Summary to a Heading will make the code invalid.
But what about the gazillion accordion plugins that have heading?
Simple: they don’t use the semantically correct and simple <details> HTML tag. Instead, they use divs and JavaScript to create their own accordion effect.
