clarify the suitability of system-ui

Author: NightFurySL2001

css-fonts-4/Overview.bs

@@ -638,7 +638,8 @@ Generic font families</h4>
 			or ''lang="ja"'' in Chinese locale). 
 			Some operating system vendors does not offer means to customise ''system-ui'', 
 			unlike UAs that generally allow users to customise the generic ''sans-serif'' or ''serif'' font family.
-			As the name implies, ''system-ui'' is intended for use with UI elements in web application, and not for large paragraphs of text or articles.
+			As the name implies, ''system-ui'' is intended for use with UI elements in web application, 
+            and may or may not be suitable for large paragraphs of text or articles depending on operating system vendor implementation.
 
 		<dt id="math-def"><dfn for=font-family>math</dfn>
 		<dd>