Unfortunately in the CSS implementation of oklab Chroma takes priority over Lightness, so if you have high Chroma and Lightness at 100% that results in a color

Unfortunately in the CSS implementation of oklab Chroma takes priority over Lightness, so if you have high Chroma and Lightness at 100% that results in a color outside the RGB gamut, it will not give you white, but the lightest color with that Chroma. To me this is quite counterintuitive.