Field non-uniform dimensions affect outcome

This is interesting, if I emit from a sphere and set the velocities in a Field Magma the velocities will be different if the dimensions of the Field Magma is a Cube (uniform dimensions, 50x50x50) or a Cuboid (non-uniform dimensions, example 50x100x50). I don’t really mind but until I found out through experimentation, I was a bit confused by my results.

So my question is (as well as letting people know), is this by design?