https://docs.google.com/document/d/1025uXR2A4W5cOl08c74yyTAfnP2z2upQdFdywZTtyEw/edit?pli=1
I haven't put much thought into the truck moving from one side to the other. When I first read that, I assumed WH meant he had parked the truck on the left side of the driveway when he dropped it off in the morning, and then when the girls returned from school the truck was on the right side of the driveway. That just means AJ (or someone) drove the truck at some point, that's all that it means. IMO he stressed that to try to prove his gas station story, like the audience was supposed to think, "clearly AJ drove to meet WH at the gas station, the truck had moved."
This explanation doesn't fit perfectly with his statement, but it was my first thought when I saw it. Not much of what he says fits perfectly with the other things he says anyway. So I kinda ruled that comment out as being valueless; no way to prove it, no way to know if it's even significant, no way to know what WH even meant. JMO.