Mileage accuracy in motor homes?

(Moved from Introductions)

I've recently read a statement from motor home dealer which said that mileage stated on motor homes is never the actual miles travelled. 

We are in the process of buying our first used Pilote and were impressed by the low mileage for its age. 

Can we trust the milometer on the vehicle, or is there any truth in this statement?  Or does it mean that dealers lie...?

(Can't wait to pick it up and escape.....)