Should I and how can I avoid update pulled by Google

tl:dr

OP's device is on 7.0, whereas this update is for 7.1.1 as explained here

Hence, OP needn't be concerned about it and apply pending OTA updates

For those on 7.1.1

According to Google is Rolling Back Nexus 6 Devices to Android 7.0 Nougat, ( also mentions the problems you linked to ),this update is to roll back To 7.0 , thus, enabling future OTA updates. It quotes Google manager in a reddit

There was a recent OTA update for Android 7.0 that is causing confusion for some Nexus 6 users. For those of you that want to guarantee future OTA updates, you will need to get back on the 7.0 supported track. If you are experiencing issues after accepting the 7.0 update, please factory reset your device to help resolve any problems.

For any Nexus 6 users that want to continue flashing/sideloading future builds, you can stay on 7.1.1 and continue to do so.

So, if you are willing to downgrade and get OTA updates in future, You should apply this update or flash manually updates if you want to continue on 7.1.1

As you can see on reddit, this appears to be a first, where an update actually downgrades your version !