The differences aren't all in numbers you can put on paper, though the better lap times do reflect the less obvious changes. The chassis differences between the M-lites and the full M cars directly affects how the car feels, even at moderate mostly-safe road speeds. Directly mounting the rear subframe to the body instead of using rubber bushings changes the game quite a bit. The rear axle is specific to the M cars, as well. The cost is noise and comfort, of course, but that's less of a hit on this car than some from the past.
Long story short, the old "I can mod my non-M to be as fast as a real M" misses the point of an M.