URL Redirect / Rewrite on GKE Gateway and HTTPRoute

I am attempting to set up a gateway on the Google Kubernetes Engine, where I would like to rewrite requests at /api, but I am unable to get it to work.

My Gateway is configured as follows:

apiVersion: gateway.networking.k8s.io/v1beta1
kind: Gateway
metadata:
  name: external-http
spec:
  gatewayClassName: gke-l7-global-external-managed
  listeners:
  - name: https
    protocol: HTTPS
    port: 443
    tls:
      mode: Terminate
      options:
        networking.gke.io/pre-shared-certs: "my-certificate-name"
  - name: http
    protocol: HTTP
    port: 80

And my HTTPRoute:

apiVersion: gateway.networking.k8s.io/v1beta1
kind: HTTPRoute
metadata:
  name: my-route
spec:
  parentRefs:
  - kind: Gateway
    name: external-http
  hostnames:
  - "example.com"
  rules:
  - backendRefs:
    - name: frontend
      port: 80
  - matches:
    - path:
        type: PathPrefix
        value: /api
    filters:
    - type: URLRewrite
      urlRewrite:
        path:
          type: ReplacePrefixMatch
          replacePrefixMatch: /
    backendRefs:
    - name: backend
      port: 80

What I want to do is route any requests at /api to my backend application, but I want them to be rewritten to /.

With all this configuration my routes are not getting rewritten and when I look at the events of my HTTPRoute it shows the following error:

failed: Error GWCER104: HTTPRoute "default/my-route" is misconfigured, err: unsupported filter type: URLRewrite.

I have followed the guide from google to set up URL redirects, and I don't see what I would be doing differently that would cause this error.
https://cloud.google.com/kubernetes-engine/docs/how-to/deploying-gateways#configure_url_rewrites

According to the google docs the gateway class I am using should support URL Redirects
https://cloud.google.com/kubernetes-engine/docs/how-to/gatewayclass-capabilities?hl=en

My cluster is on version 1.27.2-gke.2100

Why would I be getting an error that URLRewrite is unsupported when in the Google documentation it says it should be?

The URLRewrite in your HTTPRoute on GKE gate based on the error message is not supported. From the same documentation it shows that the GKE version is not yet supported.

I would like to suggest open issue tracker and submit concern as a feature request.