Just received December (2016) security patch as build MOB31Q.
Two problems here:
1. MOB31Q is not listed anywhere as a release from Google.
2. The December patch was supposed to be included in the Android 7.x OS update, not a stand-alone release.
The theory offered on Google's Nexus support forum is that MOB31Q is a T-Mobile-only release.
This all lends credence to the idea that T-Mobile really is sitting on the Android 7.x release for some reason.
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