Prism of Belief +n to Level of all Blink Skills is not applied to Sands of Silk's Blink skill

As title, Prism of Belief +n to Level of all Blink Skills is not applied to Sands of Silk's Blink skill.

If it’s expected logic, please add some description to head up the jewel is not applied to.
By literally it means, it should apply to.