Sending co variance data through mavros in VISION_POSE_ESTIMATE mavlink message

When I send pose data over /mavros/vision_pose/pose topic the copter is working fine in simulation. I want to send the pose with co variance using the topic /mavros/vision_pose/pos_cov since it takes PoseWithCovariance type message.
in mavros, both the topics are interpreted in the same way and the same mavlink message is populated here
but when I publish on topic, /mavros/vision_pose/pos_cov, ardupilot does not receive pose estimate.
Is there a way to send co variance data through mavros? @LuckyBird @rmackay9