Note that for non-Pixel Android phones, the Android that it is running is only part of the picture, and is permeated with non-Google code. The hardware driver code (BSP, or Board Support Package) is an external part; custom frameworks or libraries to support product specific features such as special camera configurations or AI accelerators; custom apps such as photo apps, dialers, gallery, etc; themes such as Oxygen OS or One UI; cloud services that connect to custom apps. Your Chinese tablet might be from a smaller company which does not provide many of the above, but leading Android phone companies have large SW teams which develop these SW for their products.