The only thing that is "muscle memory" really are off screen-turns / flicks like 180 degree turns etc. In other words, things that you can do with your eyes literally closed and still repeat them with a reasonable consistency for their purpose.
Whenever you turn to aim to a point on your screen accurately though in order to hit a target in a game, hand-eye co-ordination takes over and it is 100% predicated on visual acuity and eye tracking - you "watch" the target to your screen centre and your brain is constantly interpolating the motion and your hand movement to do this. Human's have had a good few million years of evolution to "hit the thing that's moving" and our brains are very good at continually adjusting our muscles and nerve signals in real time from visual stimulus in ways that we can't understand and don't even realise is happening.
There are a whole curve of sensitivities going on in front of your eyes in a video game depending on where you look on the screen, and this is even different (increasingly slower horizontally) the more your character's FOV is deviated towards either pole (i.e your view is looking up or down). No matter how much you play on the same sens, if you see an enemy at a point on your screen and then try to aim to him with your eyes closed before moving your mouse using only your "muscle memory", you will have no control whatsoever ever and wont be hitting a barn door - that's because it's NOT muscle memory! This is unlike other things we train and learn that ARE simply motor skill / muscle memory, like the dexterity in the keyboard hand to control character movement etc.
So basically, "muscle memory" as a term for anything other than off screen flicks / turns in gaming as far as aiming goes, is a myth.
So why do people like 0% then? Simply put, it makes tracking & recoil control at the crosshair feel the most familiar across different FOVs, and these are common mechanics & requirements in most aim dependent games, especially those that have "aiming down sight" mechanics for increased accuracy. It's actually a bad conversion for "muscle memory" since on any different FOV your off-screen flicks or 180s etc are always different when you match by 0%, and on the same FOV 360 distance is the same as 0% anyway (or any other percent for that matter)
My eyes were opened (pun intended) to how hand-eye co-ordination is the most important factor when I started using a custom mouse acceleration curve and my performance improved massively. This is everything "wrong" by the generally received so called "gamer wisdom" - the sens is basically always completely different all the time, depending where I look, how fast I move the mouse, the game's movement or camera rotation mechanics (3rd vs 1st person etc).... everything - yet still I am able to play extremely precisely, more than before when I was on a so called "1:1 sens".
You should use the calculator to arrive at values and create templates that you find comfortable and enjoyable to use that you can apply to different games, because it makes games feel more familiar, not because your aim is necessarily reliant on a match to be able to function. There's nothing matched about them anyway really - you are constantly adapting all the time anyway when you are playing and you can adapt to different sensitivities very quickly.