Stock 9 or 11? The device shipped with Pie, if that's the yardstick. Otherwise, current AOSP 11 standards determine it a good build.
2 steps forward and 11 steps back: To fully upgrade from the factory build, we lose custom recovery, MicroG, and ownership of /data. At present, there is no utility in updating the OS, or flashing a custom ROM for this device. Just novelty and convenience of having some UI features without rooting.