Truck Lighting/Dot Regulations

I noticed on the new Kenworth's the fender lights are Amber front and back, i purchased a 99 KW with the fender lights amber front and back and went to match it with another set of fender lights dropped down from the mirror and installed them but noticed only one side of the lights work as running lights but the directional lights work on both sides.
I asked the company I purchased them from and they responded with a DOT regulation that states you cannot have a fender light work on both sides amber with running lights, it can only work both sides as a directional.
Is that true, do the new trucks with fender lights work only have running lights on one side?

 

I thought the regulation was red to the rear and amber to the front until i noticed the new KW's with amber on both sides for the fender lights.
These lights are not on the tail of the truck, they are at the door mirror and the front of the fender, could that make a difference?

 

My W900 is like that too, i asked a PA Kenworth parts worker and he stated its just a persons preference.

 

The lights that i am questioning are not tail lights, stop lights or stop lamp or tail lamp, IMO a tail light is at the end of the vehicle.
Amber lights are lit to the rear on many trailers in the mid section, my Talbert 55 ton Lowboy has a amber light that also acts as a directional mid section on the trailer that sticks out so it can be seen from the front and rear.
The rule that you quoted 393.11 is in reference to tail lights which are at the rear of a vehicle.
Webster dictionary:
Tail Light
A usually red light at the rear of the vehicle, also called a tail lamp.