Usually, for the Pixel series, Google rolls its security updates on the first Monday of the month. However last month, many Pixel 3 and Pixel 3 XL users did not receive the December Update. While Pixel 4 and Pixel 4 XL users received the security update, it is not clear why Google did not release the update to Pixel 3 users. Now on Twitter, Google has revealed that they plan to roll out “a joint January and December security update” to those who did not receive the update in upcoming days.
We understand your concern, Mike. If you did not receive the December update, in the coming days you'll be receiving a joint January and December security update. We apologize for the inconvenience.
— Made by Google (@madebygoogle) December 31, 2019
Usually, Google is the first to provide users with the latest security update but for the last three months, Samsung managed to beat them with some Galaxy smartphones already receiving the January security patch.