MultiPlayerParticipant always has generic DisplayName()

[stolk]

I only get generic DisplayName() values for participants.
Regardless whether it is 'in circle of friends' or not.

        auto showcallback = [fetchcallback]( gpg::RealTimeMultiplayerManager::WaitingRoomUIResponse const& waitresult )
        {
                view_enabled[ VIEWBUTN ] = true;
                if (gpg::IsSuccess(waitresult.status))
                {
                        std::vector<gpg::MultiplayerParticipant> participants = waitresult.room.Participants();
                        ASSERT( participants.size() >= 2 );
                        const char* creating_participant = waitresult.room.CreatingParticipant().DisplayName().c_str();
                        const char* room_desc = waitresult.room.Valid() ? waitresult.room.Description().c_str() : "-";
                        LOGI( "Succesfully showed room (created by %s): %s", creating_participant, room_desc );
                        int slot=-1;
                        for ( int i=0; i<participants.size(); ++i )
                        {
                                const gpg::MultiplayerParticipant& participant = participants[ i ];
                                LOGI( "Participant %d: %s (%s)", i, participant.DisplayName().c_str(), participant.Id().c_str() );
                                if ( PARTICIPANT_IS_ME( participant ) )
                                        slot = i;
                                //game_services_->Players().Fetch( participant.Id(), fetchcallback );
                        }
                        ASSERT( slot >= 0 );
                        static char msg[ 256 ];
                        snprintf( msg, sizeof(msg), "paired slot=%d pc=1", slot );
                        launchmessage = msg;
                }
                else
                {
                        LOGI( "We cannot play, as we failed to show the waiting room ui." );
                }
        };

Will yield something like Player 1234 for all remote parties, instead of the real display name.