GitHub can use ID+USERNAME@users.noreply.github.com / USERNAME@users.noreply.github.com emails (https://docs.github.com/en/account-and-profile/setting-up-and-managing-your-personal-account-on-github/managing-email-preferences/setting-your-commit-email-address), which is unlikely to be known by Jenkins.

If somebody is using the github-oauth plugin, he is likely to want those emails to be resolved to USERNAME. So it would be nice if the github-oauth plugin included a GitHubPrivateEmailIDResolver, implementing https://javadoc.jenkins.io/hudson/model/User.CanonicalIdResolver.html