We have a Kazakh saying: "Little ones' shoulders stuck together." This…

We have a Kazakh saying: "Little ones' shoulders stuck together." This means that the baby is constantly lying down, gaining weight and if you don't do shoulder massage, they will stick together. How reliable do you find this information? Please share your opinion. Yesterday, aunts came over and did a massage, noticing that one of their daughter's shoulders doesn't protrude.