That does indicate good things happening in their filtering setup though. Overzealous PMs at Google push out legit spam from time to time, and the observed beha

That does indicate good things happening in their filtering setup though. Overzealous PMs at Google push out legit spam from time to time, and the observed behavior suggests that they're treating all traffic equally. To block from-Google spam you should just have to mark it as such and let the algo do its thing (other issues notwithstanding).