[css-align-3] Content can overflow even if the alignment subject doesn't overflow, so be precise about it.

Author: fantasai

css-align-3/Overview.bs

@@ -1067,7 +1067,7 @@ Content-Distribution Shorthand: the 'place-content' property</h3>
 Overflow and Scroll Positions</h3>
 
 	When the <a>content-distribution properties</a> are set
-	on a <a>scroll container</a> with overflowing content,
+	on a <a>scroll container</a> with an overflowing <a>alignment subject</a>,
 	rather than shifting the layout positions of its content,
 	they instead change its <a>initial scroll position</a>
 	so that the initially-visible content