Notify whitelist experimental feature does not seem to work

I’ve followed the instructions here to ignore all but a specific set of branches when posting notifications of build failure/fix in circle:

https://circleci.com/docs/configuration#per-branch-notifications

However, I’m noticing recently that CircleCI is still posting notifications to the webhook I have configured for branches that are not on the whitelist. For example, I have a branch “myfeature” and push that up to github where a build with circleci gets triggered. Here’s what my circle.yml looks like for notify override:

experimental:
  notify:
    branches:
      only:
        - staging
        - production

Even though myfeature is not in the ‘only’ stanza, a notification is nevertheless posted by circle.

We’re currently having the same problem. @fanwar has this feature worked at all for you since you’ve posted this?

Seeing the same issue here with the “ignore” pattern, is there a plan to resolve this?

EDIT: It’s possible my issue is only for cancellations though, like this Experimental notification hits channel for build cancellation