Nore, what does the fabric have to do with anything? I am pretty sure it is cotton but that doesn't mean what constitutes a good fit changes.
look at the first picture, the left shoulder has a little divot in the last picture, the right shoulder has one so the shoulders do not fit.
on the first and last picture, his arm sleeves look to be painted on. its like timotune's shirts.
in the first picture, you can see more of the "U" with the jacket and bowing of the lapels instead of a "V". the jacket does not hug his neck all the way around which is especially apparent on the left side of his neck. It is very apparent in the 3rd picture but a small part of that is because Nii has his hands in the jacket pockets. however, i highly doubt that being the only cause because it is clear from the 1st picture there is some bowing of the lapels. Nii putting his hands in his pockets on accentuates the problem.
again i like the use of textures with the shoes, cotton suit, tie and PS, it is far better than most in this thread. Nii is usually on point with his fits but here he dropped the ball.
Let me comment on this first by stating I am a bigger person. I wear a 38-40 waist and 44-46 Jackets. All good fitting suit jackets will fit just as NICELY as it does in Nil's post. The dimples on the shoulders are only apparent because when we lift our arms, the arms sit farther out than the shoulder bend. And when our arms are down at our sides, they fit the shoulders perfect.
@Nil, Great look, I really love the color of the suit and the fit of the jacket and pants. An inspiration look for me.