[mediaqueries] Make the language around 'does not apply' clearer.

--HG--
extra : rebase_source : 868af67080a705c8d96b7d862592bab33d1cf24e

Author: tabatkins

mediaqueries/Overview.bs

@@ -433,8 +433,9 @@ Media Features</h3>
 			<a>Media features</a> only accept single values: one keyword, one number, etc.
 	</ul>
 
-	If a media feature does not apply to the device where the UA is running,
-	that <a>media feature</a> will always be false.
+	If a <a>media feature</a> references a concept which does not exist on the device where the UA is running
+	(for example, speech UAs do not have a concept of "width"),
+	the <a>media feature</a> must always evaluate to false.
 
 	<div class="example">
 		The media feature ''device-aspect-ratio'' only applies to

mediaqueries/Overview.html

@@ -705,8 +705,9 @@ <h3 class="heading settled" data-level=2.4 id=mq-features><span class=secno>2.4.
 			<a data-link-type=dfn href=#media-feature title="Media features">Media features</a> only accept single values: one keyword, one number, etc.
 	</ul>
 
-<p>If a media feature does not apply to the device where the UA is running,
-	that <a data-link-type=dfn href=#media-feature title="media feature">media feature</a> will always be false.</p>
+<p>If a <a data-link-type=dfn href=#media-feature title="media feature">media feature</a> references a concept which does not exist on the device where the UA is running
+	(for example, speech UAs do not have a concept of "width"),
+	the <a data-link-type=dfn href=#media-feature title="media feature">media feature</a> must always evaluate to false.</p>
 
 	<div class=example>
 		The media feature <span class=css>device-aspect-ratio</span> only applies to