The so-called "muscle memory" means that the muscles of the human body have a memory effect. After the same action is repeated many times, the muscles will form a conditioned reflex. Human muscles acquire memory very slowly, but once they acquire memory, they forget it very slowly. If a person's pulling is the result of his repeated muscle memory, then the right or wrong of this action is hard to change.
The same is true of calligraphy practice. No matter the correct stroke or the wrong stroke, repeated training for a long time will form muscle memory.