The M4-2 viewfinder optics on the first M4-2 production batch are the same, the change happened somewhere in the second batch IIRC. Other elements of the camera's construction are different from the M4, including the viewfinder.
"Cheapened" is a, perhaps, inelegant way to express the differences. The M4-2 was built using more modern assembly techniques, which ensured Leica's survival by keeping prices lower and profits higher. Some bits were made less expensive (steel gears vs brass gears, plastic frame counter rather than machined metal, etc), but having owned both, I cannot see the M4-2 as being "cheapened" in feel or quality, just different from the M4.