[css-forms-1] Clarify accessibility principle

Author: lukewarlow

css-forms-1/Overview.bs

@@ -62,7 +62,11 @@ spec:css-forms-1; type:value; for:/; text:::placeholder
 
   1. The styles are identical in every user agent.
   1. The controls are recognizable and usable on their own without additional styles.
-  1. The controls pass 100% of <a href="https://www.w3.org/TR/WCAG22/">WCAG 2.2 AA standards</a>.
+  1. The controls are accessible out of the box in default configurations, ideally passing <a href="https://www.w3.org/TR/WCAG22/">WCAG 2.2 AA standards</a>.
+
+  NOTE: Authors may need to do extra adjustments to ensure their controls are accessible depending on any customizations as well as the context the form control is placed into.
+  The basic appearance does not prevent adjustments by the author that are inaccessible.
+
   1. The styles are consistent across controls…
     1. …in look & feel.
     1. …in how they are defined in code.