Let's talk about these differences. Is it you are implying that there exist a difference in the van allen belt radially along it's inner wall? Is the radiation not uniform 360 degrees around the earth?
In a very basic and simplistic view, yes, the VAB encompasses 360 degrees around Earth. Although that leaves out a lot of detail and makes a lot of assumptions.
In a more realistic, and relevant view, it is not uniform, and it has a specific, approximately toroidal shape, aka a doughnut (donut for you folks on the west of the Atlantic) aligned closely with the Earth's geomagnetic axis -
not the physical axis, ecliptic, or the Moon's orbital plane.
This torus is a
three-dimensional shape, and the extent above and below the "geomagnetic equator" is well mapped. It is relatively straightforward to calculate an orbit which travels above and below the doughnut, or which only intersects particular parts of it.
You seem to be labouring under the misapprehension that all orbits must be aligned to the same plane as the VAB, and must necessarily pass through the centre...