I don't know where they're "coming from" since I always either download the update from
Full OTA Images for Nexus and Pixel Devices | Google APIs for Android | Google Developers or download the full factory image from
Factory Images for Nexus and Pixel Devices | Google APIs for Android | Google Developers and flash it myself. (If you flash the full ROM, you delete the -w from the last fastboot line to keep all your apps and data - but the bootloader has to be unlocked for flashing the file. The update can be sideloaded from recovery.)
Why wait a week or two, when you can download the update in 2 days (Tuesday should be "update day").