Plenty of Yohji is slim. TBH if you expect any sort of consistency on that front you'll find yourself frustrated fast - I have 3s slimmer than 1s, and some size 2 trousers I could genuinely fit in twice over.
As another note, I've been in Conduit Street and suggested items from the YYF collection that the SA's thought could work - it's part and parcel of how the label designs, thinks and operates. So if you like the coat there's nothing to worry about. Looks ace.