> The HTML for this example looks roughly like this:

<style> .special { accent-color: papayawhip } </style> <input type=checkbox switch checked> <input type=checkbox switch checked class=special>

I immediately don't trust these docs nor the implementation due to the almost invalid HTML examples. Attributes with spaces require quotes around the value. Opinions that extend beyond the standards, but even to the examples is why the web is so ugly.

The way this parses is that switch and checked are attributes with no value. That is technically correct but ambiguous to humans. Unsupported browsers will just ignore the switch attribute, but adding custom attributes this way is bound to cause weird bugs if using frameworks that don't prefix the names of their custom attributes. I believe certain doctypes or serving the HTML with another content type (XML) will throw an error for not having the quotes.