who said it has to?! silly rabbit it only has to work for one number. The proof is 1 = .999... The proof isn't 1/x * x = .999... for all x
That is just a bunch of non-sense. Sure, absolute 1 or 0 does not exist in an analog scale. However 1 does exist in discrete terms. If you have 1 apple in you hand, you have exactly 1 apple in your hand (not 0.99999999999 apples).
But, absolute 1 and 0 do exist in an "analog scale." Mathmeticians doen't dispute the existence of 1. That was a mistaken comment by the OP. They are simply saying that .999... = 1.