Level surface from front axle to back

Within this video GT86 worked example, in the video (2. Setup Alignment Equipment) I can see that the ground is checked to see if it's level between the front two axles and I assume the same will be done for the rear two axles as well. My question is: Does this need to be checked between the front axle and the rear axle as well, so checked between the passenger side front wheel and the passenger side rear wheel, as well as the driver side front and the driver side rear?

The reason why I ask is because my drive way (where I tend to the alignment) is at a decline of roughly 1.5 degrees from the front to the back. So the rear axle would be higher than the front axle.

Also, how drastically would this affect camber and toe measurements, if for example the both axles are level with each other, but front axles are not level with the back?