Yes, I believe the dealer made a mistake, and that tractor is a 2008 model. As to the 4 wheel assist, that is what it is. 4 wheel assist means that the tractor has smaller gears in the front axil than it does in the rear axil.
4WD tractors with smaller tires on the front than on the rear are really 4 wheel assist. True
4WD tractors have the same size gearing and tires on the front and rear, and most are articulated tractors.