cluster_header not set for RequestMirrorPolicy

[mirwide]

RouteConfiguration always return empty cluster_header fields. Code for reproduce:

RouteConfiguration.newBuilder()
            .setName("local_route")
            .addVirtualHosts(
                VirtualHost.newBuilder()
                    .addRequestMirrorPolicies(RequestMirrorPolicy.newBuilder().setClusterHeader("cluster-shadow")))
            .build();

cluster_header exist in snapshot

but not return in RouteConfiguration

grpcurl -plaintext -d '
{
   "version_info":"1",
   "type_url":"type.googleapis.com/envoy.config.route.v3.RouteConfiguration",
   "resource_names":[                   
   "local_route"
   ],
   "node":{
      "cluster":"cluster1",
      "id":"id1"
   }
}' localhost:8888 envoy.service.discovery.v3.AggregatedDiscoveryService/StreamAggregatedResources | jq .resources[0].virtualHosts[0].requestMirrorPolicies
[
  {}
]