[css-grid-1] Clarify that fallback alignment is a 'behaves as' sorta thing. Also note that the baseline-cycle determination doesn't change over the course of the algorithm.

Author: tabatkins

css-grid-1/Overview.bs

@@ -3388,7 +3388,12 @@ Inline-axis Alignment: the 'justify-self' and 'justify-items' properties</h3>
 	(whose size is therefore dependent on both the item's size and baseline alignment,
 	creating a cyclic dependency),
 	that item does not participate in baseline alignment,
-	and instead uses its <a>fallback alignment</a>.
+	and instead uses its <a>fallback alignment</a>
+	as if that were originally specified.
+
+	Note: Whether the fallback alignment is used or not
+	does not change over the course of layout:
+	if a cycle exists, it exists.
 
 <h3 id='column-align'>
 Block-axis Alignment: the 'align-self' and 'align-items' properties</h3>
@@ -3404,7 +3409,8 @@ Block-axis Alignment: the 'align-self' and 'align-items' properties</h3>
 	(whose size is therefore dependent on both the item's size and baseline alignment,
 	creating a cyclic dependency),
 	that item does not participate in baseline alignment,
-	and instead uses its <a>fallback alignment</a>.
+	and instead uses its <a>fallback alignment</a>
+	as if that were originally specified.
 
 <h3 id='grid-align'>
 Aligning the Grid: the 'justify-content' and 'align-content' properties</h3>