Why we have nesting of where in dl ol ul ? ( :where(dl, ol, ul))

Why do we have a double nesting of where for dl,ol,ul ?

:where(dl, ol, ul) :where(dl, ol, ul) {
  margin-block-end: 0;
  margin-block-start: 0;
}

Actualy that's not working for only 1 nesting like : 
<dl>
  <dt>Coffee</dt>
  <dd>Black hot drink</dd>
</dl>


https://github.com/csstools/normalize.css/blame/a4a0c202e8b34426e0cd8e0411005906cd94e407/normalize.css#L36