Hello GrinGEO,
If you export OBJ in WGS84 coordinates, each vertex will have XY in degrees and Z in meters.
In case the post processing application that you are using cannot work with such geographic systems, they will be just considering all XYZ values are of the same scale and units. Therefore you will be observing a ray of points along Z axis, since X and Y values wouldn't change much (only some lower decimal digits are changed for the degrees).
As for the number of vertices, are all of them inside the bounding box and whether the boundary is applied for export?