I'm in the middle of a cleaning/wax job right now and I'm intersted in this too.
Not that I'm necessarily right, but my hunch is that you're seeing the light reflect different in the ball travel area due to the slight depressions made by the ball. In the return lanes and ball guide areas the ball is pretty much always taveling over the exact same spot. I always assumed that there's not much more you can do about it other than cleaning off the dirt trial and waxing. Maybe clear coating the playfield? I don't know.
And yeah, you're probably being too picky, haha.
Roselle, IL
Auckland, NZ
