indeed shadows are not white, but the added effect of a drop shadow can be any color, so where i see your point i think your wrong. doesnt matter the color.
for the 3d i think that it is just a way people think is cool and trendy. even though it has no one perspective to it or and parallel directional i see it as a more or a new effect per say and less of an illusion to make the piece appear 3d. the way i see it, the applied 3d to each individual bar is a complimentary angle to said bar. for example taste fua att recently did a piece for a competition i think demonstrates this.