“It improves your muscles stronger” is not a benefit of improved flexibility.
Explanation:
The flexibility tends to increase the muscle flexibility with actin filament and tendon to exceed the limit of stretch and to return to its original position which leads to the growth of filaments. With the growth of filaments, muscles grow.
And with the growth of muscles in an area, makes the muscles be strong. And hence, the flexibility improvements lets not the muscle be stronger. This let to increase the joint movement too and secures from getting the injury by increasing range of motion.