Alpha vs RGB

I’ve got a texture where the blue channel and the alpha channel have the same information. I have literally copied the alpha-channel data into the blue channel.

Yet, if I do this inside Unity:

    fixed4 c = tex2D(_MainTex, IN.uv_MainTex);
    o.Albedo = lerp(c.a, c.b, _Lerp);

And then play with lerp, these two will look different (the blue one will be darker).

Why is this?

Ok, answering my own question. This has to do with sRGB and gamma stuff:

Bypass sRGB sampling

Checking this will make the color information be the same.