Not sure where you're getting this info but it's completely incorrect.
YSL E commerce in USA is really only run by one person and she handles every order individually which is why it takes a while to process.
There are no buyers at the boutiques, they receive items based on what the house wants to represent. Yes the styles are based on region and location, which is why SLP LA will have more casual goods than NY, but it's all based on what the house sends them. There are managers there but they don't do any of the buys. Most of the people at SLP boutiques are about as in the know as you and I.
Also the exclusive styles that some stores may get aren't really from SLP but from Kering. They end up releasing accessories and other items from their factories and slap the labels on. There is a noticeable difference in items sold by mr porter/yoox and at the actual boutique.