I think that depends somewhat on the material you choose for the top sheet.
I built my (non-torsion box) table with a plywood top sheet. Within 3-5 hours of use. ruts started to develop where the roller wheels ran, especially near YMin, where most of the motion occurred. 
That plywood (Factory Select grade) was really soft!
I threw a sheet of 3/8” MDF on top, and after many hours, there aren’t any signs of ruts or grooves.
But I agree, a metal running surface isn’t a necessity. MDF will work fine!
I posted something similar (not an actual torsion box, but definitely grooved). Was it that post that you saw?