Some Google Pixel 3 and Pixel 3 XL smartphone owners have been reporting that the March update for their devices has optimized read/write storage performance to a considerable degree. Images of AndroBench comparisons between February's update and March's update show some benchmark results drastically improving.
https://www.notebookcheck.net/Some-Google-Pixel-3-owners-are-reporting-improved-storage-performance-after-latest-software-update.412255.0.html