Has anyone tested the new setting "Save Uncompressed HDR screenshots as AVIF" Slider under Steam>Settings> In Game> Screenshots?

Unfortunately function isn't working for me, and still saving uncompressed screens washed out as PNG. Unless Steam is saving into a different location then my selected folder for Separate Uncompressed Screens, that went undetected in my complete system search...IDK..

Also I've searched online for more specific info about this New Setting with no direct hits..