Incorporate Emil's changes

Co-authored-by: Emil Lundberg <emil@yubico.com>

index.bs

@@ -2787,7 +2787,7 @@ Note: Invoking this method from a [=browsing context=] where the [=Web Authentic
 
 Upon invocation, the [=client=] employs a [=client platform=]-specific procedure to discover availablity of these capabilities.
 
-This method has no arguments and returns a map of capability keys to boolean values. 
+This method has no arguments and returns a map of capability keys to Boolean values. 
 
 <xmp class="idl">
     partial interface PublicKeyCredential {
@@ -2800,11 +2800,12 @@ This method has no arguments and returns a map of capability keys to boolean val
     };
 </xmp>
 
-Keys in {{GetClientCapabilitiesResult}} SHOULD be members of {{ClientCapability}}.
+[=map/Keys=] in {{GetClientCapabilitiesResult}} MUST be sorted in ascending lexicographical order.
+The set of [=map/keys=] SHOULD equal the set of [=enumeration values=] of {{ClientCapability}}.
 
 When the value for a given capability is [TRUE], the feature is known to be currently supported by the client.
 When the value for a given capability is [FALSE], the feature is known to be not currently supported by the client.
-When a given capability is `undefined`, the availability of the client feature is not known.
+When a capability does not [=map/exist=] as a key, the availability of the client feature is not known.
 
 Note: Invoking this method from a [=browsing context=] where the [=Web Authentication API=] is "disabled" according to the [=allowed to use=] algorithm&mdash;i.e., by a [=permissions policy=]&mdash;will result in the promise being rejected with a {{DOMException}} whose name is "{{NotAllowedError}}". See also [[#sctn-permissions-policy]].