Potentially inaccurate README note on webhooks & forks

[mdb]

The README reads:

Note on webhooks: This resource does not implement any caching, so it should work well with webhooks (should be subscribed to push and pull_request events). One thing to keep in mind however, is that pull requests that are opened from a fork and commits to said fork will not generate notifications over the webhook.

However, I'm not 100% certain this is accurate & may be leading users to configure aggressive check_everys that generate excess load on both GitHub and their Concourse instance. Based on my research, both of the following successfully generated webhooks:

1. open a pull request from a fork requesting to merge my-fork/repo:some-topic-branch to upstream/repo:master.
2. push a subsequent commit to my-fork/repo:some-topic-branch after the step 1 pull request had already been opened.

Is it possible the above-quoted README note is incorrect?

Thanks!