The calendar just flipped over to March, which means there is a new security patch on the way in the next few days, and apparently Vodafone thinks that it will be heading out to the Nexus 6P next week. Now this isn't a huge surprise considering Google does typically release this security patch during the first full week of the month (this is why it usually doesn't hit on the 1st of the month), which would be next Monday or Tuesday. Now typically the update will head out to devices within a day or two of Google releasing the full system images and OTA's for sideloading, as well as the security bulletin detailing what was fixed.
Since Vodafone says that the Nexus 6P will get the update on March 7th, that doesn't mean that the other Nexus and Pixel devices won't be getting the update at the same time. Remember the majority of Nexus and Pixel devices besides the Nexus 6P and Nexus 5X, that Google are still supporting with these releases, were not sold by carriers in the US and most other countries. Therefore Vodafone really has no idea what's happening with updates to these other devices. So keep in mind that the Nexus 6P and other devices will be getting the update next week.
Google has been releasing monthly security patches for a little over a year now. They started doing this due to the number of vulnerabilities that were being found in Android - and these were serious vulnerabilities too. Google has been updating devices that don't even get operating system updates anymore, which is a pretty big deal. Since most people don't upgrade their phone every year and some don't update it every other year. Manufacturers have been doing their best to keep up with Google and pushing out these updates, but of course, with the number of variants and having to deal with carriers, Google has been updating more frequently than Samsung, LG, HTC and a few other major manufacturers.
Next week, look out for an update hitting your Nexus 6P, Nexus 5X, Pixel C, Pixel and Pixel XL smartphones. It should fix a few vulnerabilities on your devices.