^size down 1-2 only for raw b/c they stretch. For washed, go TTS or maybe 1 size down depending on the model. Most diors (even 17.5cm) are fairly loose through the leg when wearing the correct waist size IME but that's b/c I have skinny legs. The models Hedi Slimane used are especially thin (and tall), which make all the jeans look loose/slouchy.
edit: in that 2nd pic you can tell he's wearing them on his hips, not waist, so def. not sized down