I wonder if you still remember that in March Google pushed a downgrade of OTA update for Nexus 6, which brought the Android 7.1.1 system back to version 7.0. Now a few months later, the machine has started receiving Android 7.1.1 updates.
Nexus 6 Push Android 7.1.1 Update again
Note that you need to use the latest version of Android 7.0 to successfully install Google push the latest 7.1.1 update, the new version of the volume around 370MB.
reported that the March Android 7.1.1 Update made Android Pay unusable, so Google had to push for a downgrade update.