Watcher HTTP request when using traffic filters?

[Jared_Wallace]

I'm having some trouble getting Watcher HTTP requests to function when using traffic filters on Elastic Cloud Enterprise.

A Watcher with the following block works perfectly, returning 200s as expected on a fresh Deployment, where foo.es.endpoint.io is the ES endpoint retrieved from the Deployment dashboard.

{
  ...
  "input": {
    "http": {
      "request": {
        "scheme": "https",
        "host": "foo.es.endpoint.io",
        "port": 443,
        "method": "get",
        "path": "/_cluster/health",
        "params": {},
        "headers": {},
        "auth" : {
          "basic" : {
            "username" : "username",
            "password" : "password"
          }
        }
      }
    }
  },
  ...
}

My trouble starts when adding a Traffic Filter (say a GCP private link filter or IP filter), which results in the Watcher returning 403s. I imagine this is because the endpoint isn't resolved internally.
Does anyone know how to make this work on Elastic Cloud through the traffic filter, or staying 'within the deployment' internally?