It is for texture surfaces for 3D modelling.
#1
We use square pixels in our textures, even when the output is non square. The only time that's not done is when we're working with non square source texture.
#2
Well, that's fine, but what if you want layer effects (such as glows) which are proportional to the non-square pixels in your output? I you know a texture will be used 2:1, for example, then you'd like a bevel or emboss or shadow to be scaled 1:2 in the source.
#3
No, layer styles are not going to easily handle non-square aspect ratios. Too many of the calculations are based on distance between pixels, and would be very, very difficult to make work in non-square pixels.
#4
Thank you Chris. I suspected it was so, but now I can stop looking for a solution other than flattening and rescaling.
#5