If you are going in 80miles per hour, you are going 80 miles per hour, and it will take you one hour to go 80 miles, nothing related to how much airpressure you have. The question is hypothetical, not practical. He never said by car, so he could have have the example in the air, or even space.
But, if he were to say the speedometer shows 80 miles per hour, how fast are you "really" travelling at, then yes, tire pressure is relevant, as well as the thickness of the rubber on your tires, not to mention if its a different sized wheel compared to "original speccs".
Not to mention she prooves she doesnt understand shit when she starts involving the weight of the "truck" having anything to do with it.