Mr porter E-mailed back and mentioned that it's meant to be a bit longer to look 'distressed' and to compensate for the short length through the body. It's 100% silk so it doesn't stack very well through the arm, and it bunches up towards the sleeve.
Does it look alright? I wore a shorter t-shirt that I own to match the short torso length of the jacket. I wonder if I can get the sleeves shortened somehow? There is elastic ribbing on the wrist, so might need to be taken up in the shoulder?
This is the model pic from Mr. Porter.
This is a pic if I let it hang over my hands: