For older Google phones (as well as most other Android ones) it is the standard. (AFAIU this was mostly due to Qualcomm’s policies and lack of pushback from Google et al.) Newer Google ones get 5–7 years[1], and Samsung has also switched to a similar support term (but keep in mind that only Samsung’s flagships get monthly security updates).
[1] https://support.google.com/pixelphone/answer/4457705