[css-anchor-1] Make it clearer that the automatic anchor positioning stuff only applies when the anchor(auto) is used validly.

Author: tabatkins

css-anchor-1/Overview.bs

@@ -133,7 +133,7 @@ The ''anchor()'' function has three arguments:
 
 	The <dfn value for=anchor()>auto</dfn> keyword
 	indicates [=automatic anchor positioning=].
-	See [[#auto-anchor]] for details.
+	See [[#anchor-auto]] for details.
 
 	The physical <<anchor-side>> keywords
 	(<dfn value for=anchor()>left</dfn>,
@@ -284,14 +284,15 @@ causing the element to automatically stick "next to" the [=anchor element=]
 in the most obvious way,
 and flip to the other side if necessary.
 
-[=Automatic anchor positioning=] is only valid
+[=Automatic anchor positioning=] is only active
 if the opposite [=inset property=] is ''top/auto''.
 (For example, if an element had ''top: anchor(auto);'',
 it would have to also have ''bottom: auto;''.)
 If this is not the case,
-the ''anchor()'' function represents an [=invalid anchor query=].
+the ''anchor()'' function represents an [=invalid anchor query=],
+and the element does not use [=automatic anchor positioning=] in that axis.
 
-When used in a given [=inset property=],
+When using [=automatic anchor positioning=],
 the ''anchor()/auto'' <<anchor-side>>
 behaves as the opposite side of the property it's used in.
 That is, when used in ''top: anchor(auto);'',