Docs feedback: distributed container registry mirroring in AWS autoscale setup

https://docs.gitlab.com/runner/configuration/autoscale.html#distributed-container-registry-mirroring

is either incomplete or incorrect or I do something wrong...

I've done the aws autoscale setup, then added my own registry mirror on the persistent instance. When I add the following snippet:

      "engine-insecure-registry=172.[MASKED].[MASKED].[MASKED]:5000",
      "engine-registry-mirror=http://172.[MASKED].[MASKED].[MASKED]:5000",

It seems the configuration isn't passed to docker-machine. I run docker system info in my pipeline using dind.

Insecure Registries:
 127.0.0.0/8

As we can see, there isn't new entries for the insecure registry or the registry mirror.

If I just use docker without gitlab or docker-machine:

{
  "insecure-registries" : ["172.[MASKED].[MASKED].[MASKED]:5000"],
  "registry-mirrors": ["http://172.[MASKED].[MASKED].[MASKED]:5000"]
}

and get as expected:

Insecure Registries:
 172.[MASKED].[MASKED].[MASKED]:5000
 127.0.0.0/8
Registry Mirrors:
 http://172.[MASKED].[MASKED].[MASKED]:5000/

It seems to me something wrong in gitlab-runner/docker-machine interactions?