[scroll-animations-1] names declared with timeline-scope are locally trapped #7759

See #8906 (comment)

Author: fantasai

scroll-animations-1/Overview.bs

@@ -1260,36 +1260,37 @@ spec: cssom-view-1; type: dfn;
 		Animation type: not animatable
 	</pre>
 
-	This property declares the scope of the specified timeline names,
-	allowing a named timeline
+	This property declares the scope of the specified timeline names
+	to extend across this element’s subtree.
+	This allows a named timeline
 	(such as a [=named scroll progress timeline=] or [=named view progress timeline=])
 	to be referenced by elements outside the timeline-defining element’s subtree--
 	for example, by siblings, cousins, or ancestors.
+	It also blocks descendant timelines with the specified names
+	from being referenced from outside this subtree,
+	and ancestor timelines with the specified names from being referenced
+	within this subtree.
 
 	Values have the following meanings:
 
 	<dl dfn-for="timeline-scope" dfn-type=value>
 		<dt><dfn>none</dfn>
 		<dd>
-			No change in name timeline scope.
+			No changes in timeline name scope.
 
 		<dt><dfn><<custom-ident>></dfn>
 		<dd>
-			Declares the name of a matching named timeline defined by a descendant
+			Declares the name of a matching named timeline defined by a descendant--
+			whose scope is not already explicitly declared by a descendant using 'timeline-scope'--
 			to be in scope for this element and its descendants.
 
 			If no such timeline exists,
 			or if more than one such timeline exists,
 			instead declares an [=inactive timeline=] with the specified name.
-
-			Note: This property has no effect if a matching named timeline
-			is defined by this element itself.
 	</dl>
 
 	Note: This property cannot affect or invalidate any timeline name lookups
 	within the subtree of a descendant element that declares the same name.
-	However, it can prevent matching timelines defined on an ancestor
-	from being referenced by this element or its descendants.
 	See [[#timeline-scope]].
 
 # Changes # {#changes}