User blog comment:Jopjopjop/High School DxD BorN episode 3 review/@comment-1359322-20150418154231/@comment-1359322-20150418164520

Well because Ise only unlocked the wings after the JD. Prior to that Ise's BB doesn't have wings. In a sense, you can say that the wings is Issei's "power-up" in Volume 7.