It should not. For 5-6 decades most auto manufacturing world-wide is based on model year and this usually transitions by the fall. Now-a-days it seems the transition occurs in the preceding summer. Model year, as stated by the manufacturer, is chiefly how insurance, taxation and value/depreciation is based. I would think 98% of people would agree that September '17 production is a 2018 vehicle - especially if stated as such. Now, I've sometimes wondered about the 6-12 months a new vehicle might be sitting on a dealer lot garnering oxidation, mildew, acid rain, bird crap etc. Well, most people probably don't wonder about that or attempt to figure that out...