[scroll-animations-1] Generalize note about operating on the flat tree. w3c#8192

Author: fantasai

scroll-animations-1/Overview.bs

@@ -94,6 +94,10 @@ spec: cssom-view-1; type: dfn;
 	by implementing the CSS features to behave
 	as if the underlying programming interfaces were in place.
 
+	Like most operations in CSS besides [=selector=] matching,
+	features in this specification operate over
+	the [=flattened element tree=].
+
 ## Relationship to asynchronous scrolling ## {#async-scrolling}
 
 	Some user agents support scrolling that is asynchronous
@@ -762,9 +766,6 @@ spec: cssom-view-1; type: dfn;
 	In case of a name conflict on the same element,
 	[=scroll progress timelines=] take precedence over [=view progress timelines=].
 
-	Note: Like most operations in CSS besides [=selector=] matching,
-	timeline scoping occurs over the [=flattened element tree=].
-
 	ISSUE: Do we want to expand this scope to preceding siblings and/or distant cousins?
 
 ## Animation Events ## {#events}