Usually, benchmark tools listings are used to spot newly and still unreleased devices and perhaps unearth some of the key specs like chipset, RAM, screen, camera, etc. This time around, however, a GFXBench listing tells us that Samsung, or at least someone, is testing the Galaxy S9+ with Android 9.0 Pie. According to the report, the device is running the latest version of Google's mobile OS and an "invalid Android Samsung-ss Edition" software on top. Probably Samsung's Experience UI that's currently unrecognizable by the benchmark app. Anyway, there's nothing else we could gather...
Source: https://www.gsmarena.com/samsung_galaxy_s9_running_android_90_pie_shows_up_on_gfxbench-news-32986.php