It's possible I wasn't specific enough when I said "graphics". Typically I blend in CIELAB when interpolating between colors for visualizations (eg data science).

But I'm unaware of rendering engines that do alpha blending in something other than linear or SRGB. Photoshop, for instance, blends in sRGB by default, while renderers that simulate light physically will blend in linear RGB (to the best of my knowledge).

It depends on the GPU and the implementation, but I personally would not want to spend the compute on per-pixel CIELAB conversions for blending.