GitHub exposes everyone's email address in GIT commits (opens in new tab)

Yes, it is a GIT feature/issue. Github does nothing to protect users (by default) from using their personal email in commits. It is definitely not well known though because almost everyone is using their private email address. Go to any big repo and you can see everyone's email.

This is more about education and changing a default.

This isn't about contacting people or communicating the status of a Github project. Github issues are fine way to communicate. If the repo owner isn't responding to issues, I don't think sending email to someone's personal email found through GIT commits is a good option. There is a reason we don't just have everyone's personal email on their Github profile. People don't want spam from people they don't know.