Add note about platform authnrs as roaming authnrs

index.bs

@@ -2350,6 +2350,11 @@ to as <dfn>roaming authenticators</dfn>.
         <dfn>roaming credential</dfn>.
 </ul>
 
+Some [=platform authenticators=] could possibly also act as [=roaming authenticators=] depending on context. For example, a
+[=platform authenticator=] integrated into a mobile device could make itself available as a [=roaming authenticator=] via
+Bluetooth. In this case the [=client=] would identify it only as a [=roaming authenticator=], and not as a [=platform
+authenticator=].
+
 The primary use case for [=platform authenticators=] is to register a particular device as a "trusted device" available as a
 [=something you have=] [=authentication factor=] for future [=authentication=]. This gives the user the convenience benefit of not
 needing a [=roaming authenticator=] for future [=authentication ceremonies=], e.g., the user will not have to dig around in their