While the regular OS update brings in new features, the security makes your device secure. Google follows the same 2 years guaranteed updates and 3 years of guaranteed security patches or updates. Which means that the Security update support for the Google Nexus 6P and Nexus 5X should have ended by September 2018 (After 3 years of launch.)
It is not the case this time. The search giant has extended the security update support for the Google Nexus 5x and Nexus 6p until November 2018 which is 3 months more than the previously guaranteed date. Google hasn’t added any reason for extending the update. However, we can assume that it could be because of the launch of Android P, but let’s not claim.
We can’t say anything unless we get an update from Google regarding this, but it’s a good thing that a device which is more than 3 years old will get a security update. We’re trying to get in touch with the Huawei and Google Team and would keep you posted as we get updates from them.