16:9 image format to 21:9 without black bars with +mat_wide_pillarbox 0.

In recent patch (Season 24) devs changed, how ultrawide monitors handle other image formats, than their native 21:9 with DX12 api. With default settings, the image is not stretched and it shows black bars on sides of the screen. This can be fixed with +mat_wide_pillarbox 0 launch argument, which should make image stretched (as written in patch notes for Season 24). Unfourtanetly even after using this launch argument my game still shows black bars. I'm launching game from Steam. Does it only work with EA app, or with Steam?  I tried many fixes and i cant  make it work again as before. Does anyone know the trick? Please help.