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
[
 {}
]