When a PR is created by an author that has a Gerrit account, they are added as a reviewer to their own CL. Since the CL has a reviewer, gerritbot then does not apply autoreviewers.

For example: https://go-review.googlesource.com/c/go/+/156297

Maybe the answer is to add them as CC, not as reviewers. I'm not sure why that's the current behavior, but it might be an automatic Gerrit behavior, similarly to how it adds reviewers if it detects them listed manually as Reviewed-By.

/cc @andybons