As an interim solution, you can add a cloud code script or a post-hook to retrieve the missing data, using the profileIds found in the request.
https://getbraincloud.com/apidocs/apiref/#capi-friend-getsummarydataforprofileid
...
"pendingMembers": {
"382eb04f-f80c-4bfc-9a12-fca508cad476": { // <- These profile ids
"role": "MEMBER",
"attributes": {},
"pendingReason": "ASKED_TO_JOIN"
}
}
...