Something just doesn't seem right about the soft overhead lighting being his only source.
I would say that the bounce seen in his glasses was angled up from in front of him and used as a fill. Angle of incidence equals the angle of reflection. His glasses are angled down so to get a reflection straight into camera the source would have to be angled up.
There is a lot of shadow in the camera right of the subject which is why I would say that the soft source is coming from high above camera left.
I guess the best way to put it is that there are infinite ways to light a shot. What works for one person doesn't work for another.