Actually, reread your own section. Passenger cars are treated differently than "trucks and vans" which are not defined other than: "In the case of a truck or van, clause (ii) shall be applied by substituting 'gross vehicle weight' for 'unloaded gross vehicle weight'."
From my reading, it seems that "trucks and vans" get to count loaded weight in their GVW.
If business vehicles are passenger automobiles, they are listed property and are subject to limits on the amount that can be deducted for regular depreciation, as a bonus depreciation allowance, and as a Sec. 179 expense.
www.thetaxadviser.com
These people seem to agree: "Significantly, for autos, the 6,000-pound limit is based on the unloaded gross vehicle weight of the auto, while for trucks and vans, the 6,000-pound limit is based on loaded gross vehicle weight, which includes passengers and cargo. This means that most full-size pickups and larger vans will be over the 6,000-pound limit and not subject to the Sec. 280F depreciation limits."