I’m worried about the same thing after I personally experienced the space gray on the side of my iPad Pro rubbing off due to a slightly loose case with rubber grips. While it made it easy to remove, never really did for about 2 years, it allowed slightly movement to rub against the surface.
In your case, 3 months seems really really quick. You would think store displays would show signs often.
Can you recall anything unique about your situation? Like how often do you use your MacBook in laptop mode? 8+ hours a day, or very little? Do you use any lotions, sunblock, or any other stuff applied directly or through secondary contact? Are your hands rougher than usual? Do you where gloves frequently, for cold, while working, etc?
With every using hand sanitizer frequently, could not letting hands dry enough before contact cause this over time? But I figure that would be a bigger issue by now.
Just throwing these ideas out to see if there is some variable in your situation that accelerated this in 3 months times, or no matter what happened, should this be considered unreasonable wear and tear in such a short amount of time and defective?