I believe that the truth would be , they don't know for sure where the Newmar employee mounted it; and they're afraid to say that!
Freightliner won't know because they didn't install the dash portion of the A/C .
Evans won't know , because even if they supplied a relay with the unit , they shipped it to Newmar in a big box with the whole HVAC assembly.
The Evans schematic I have that came with my vintage unit doesn't even have a relay shown.
But I know for a fact I have one , because I followed the wiring from the Newmar installed circuit breaker ( marked dash air conditioning) until I found it. Hidden; unmarked ; on the firewall behind a bundle of other wiring. Same thing for the low pressure switch , hidden behind wiring.
What I'm trying to say is even if someone with the exact same unit as you comes in and says where his is , unless the same employee happened to have mounted the relay in his favorite place , the description you receive could be out by 3' or more.
I would think that the wiring Newmar does on there newer coaches is way better than mine , but some things are still in the hands of the final installing employee.
Take a deep breath and look things over again , follow the wire from the thermostat to the pressure switch then from the pressure switch , see if you can find where that wire joins the Freightliner chassis harness , my relay was after the pressure switch , and before the chassis harness.
EDIT: About the only question to as Newmar about your issue would be
" Do you ( Newmar ) install a relay along with the dash HVAC assembly wiring ?" Hopefully you can get that answered.