Since the Xiaomi Mi 8 and Mi 8 Explorer Edition already got Android 9.0 Pie, seeing the Mi 8 SE on Geekbench with the latest Android update onboard is not surprising at all. However, this only means that Xiaomi has begun testing the update and it might need at least a few weeks before being ready for launch.
https://www.notebookcheck.net/Android-Pie-driven-Xiaomi-Mi-8-SE-hits-Geekbench.354261.0.html