Empty value for dst_zone label in linkerd-proxy metrics

[slimes28]

Hello,
I see that linkerd-proxy container produces almost identical series with different values for one of the metrics, the only difference is that 1 series has a dst_zone label which has an empty value

tcp_write_bytes_total{direction="outbound",peer="dst",target_addr="13.1.178.159:9092",target_ip="11.5.128.184",target_port="9092",tls="no_identity",no_tls_reason="not_provided_by_service_discovery",dst_namespace="live",dst_pod="kafka-0",dst_serviceaccount="kafka",dst_strimzipodset="kafka"} 3458189932

tcp_write_bytes_total{direction="outbound",peer="dst",target_addr="13.1.178.159:9092",target_ip="11.5.128.184",target_port="9092",tls="no_identity",no_tls_reason="not_provided_by_service_discovery",dst_namespace="live",dst_pod="kafka-0",dst_serviceaccount="kafka",dst_strimzipodset="kafka",dst_zone=""} 3183033

The question is why it is empty and what is the difference between those 2?
Using relabeling, I can't set a custom value for empty dst_zone because it will set it for both of these series. Maybe it can be done when metric is generated to not cause any issues?