Women have a greater potential for flexibility in their joints, which is due to the estrogen that flows through their veins. Estrogen helps maintain muscle elasticity and improves muscle tone, which is why it's one of the leading contributors to increased range of motion. This can be attributed to the fact that women are typically smaller in stature than men, so the muscles have less weight to stretch over which naturally increases their range of motion.
In addition, women's ligaments are also more elastic than men's, which allows for a greater range of motion. Ligaments are the bands of tissue that connect bones to other bones and help stabilize joints. The elasticity of ligaments allows them to stretch without tearing and this increased range of motion can be beneficial in preventing injuries. For example, if you are prone to ankle sprains, having more flexible ligaments can help minimize the risk of injury.
Although men do have some advantages when it comes to flexibility (e.g., they typically have more muscle mass), women generally have the edge when it comes to the range of motion. This is due to a combination of physiological anatomical factors including the presence of estrogen.