So once you declare a sampler;

Texture entskin2; //uses the stored entskin image 2

Sampler reflective
{...}

...

Float 4 reflective_pixels tex2d(reflective,...)

Specular_strength = reflective_pixels.r; //looking up the red channel
specular_falloff = reflective_pixels.g; //looking up the green channel
Specular_bounce = reflective_pixels.b; //looking up the blue channel
Cubic_strength = reflective_pixels.a; //looking up the alpha channel

Does it uses more gpu processing time to go through each RGBA value? Compared to

Float reflective_pixels tex2d(reflective...). // a single float
Specular_strength = reflective_pixels;