User blog comment:Jopjopjop/Volume 19 Spoilers/@comment-24173056-20141122062809/@comment-24468758-20141122183227

Vali's SG is his pair of wings, whereas Issei's are part of his SG's BB so he might be able to access them while only using the gaunlet but he needs to activate his SG to use those wings as he also can't access any other BG related abilities without it.