My best guess for HTTPS grades, is the ssl labs score.
https://www.ssllabs.com/ssltest/
Update: the source code says it is reaching out to this site for HTTPS:
The Obs. would make sense for:
https://observatory.mozilla.org/
There is a GitHub issue that explains this too.
https://github.com/TheKinrar/instances/issues/117#issuecomment-1319892525