Comfort is not the same as capacityWhy the Largest Passenger Number Is Not the Best Booking Rule
Published seating capacity is useful as a starting point, but airport transportation has a cargo problem that ordinary local trips do not. A party may fit in the seats while its checked luggage does not fit safely in the cargo area. That is why vehicle selection should use both passenger count and a realistic packing list.
If the provider recommends moving from the Lincoln to the Suburban, or from the Suburban to the Sprinter, ask whether the reason is people, luggage or oversized equipment. That explanation makes it easier to judge whether the larger vehicle is necessary rather than treating the upgrade as an automatic upsell.