The current "Media Queries Level 4" spec does not have a "media_query_list" production; instead it has a "<media-query-list>" production.

Also the HTML spec says, "A string is a valid media query if it matches the media_query_list production of the Media Queries specification." which is kind of confusing/misleading, since what it allows  (I think) is actually a list of media queries, not just a single media query.

So I suggest the spec instead define this requirement with the prose "...is a valid *media query list* if it matches..." and with the text of the hyperlinked references to that definition (e.g., for the "media" attribute) also changed to read "valid media query list".

I base the all the above on assuming that the spec actually intends for a media query list to be allowed throughout, not just a single media query. But if that's wrong and a single media query is what in fact should be allowed, then the definition should be changed to "media query" and the MQ spec reference should be to the <media-query> production.