User blog comment:EvanDude345rv5/Fairy Tail 353 : Nine Ghost Gate/@comment-3424593-20130928223035/@comment-7418318-20130929095154

No.

Those Zeref cultists just used Jellal as slave labour for digging up rocks and building their turret. He only learned to use magic when Ultear took over his mind, at which point he killed all the remaining Zeref cultists.

With his subordinate Ultear controlling Jellal and by extension the entire island, the Tower of Heaven just made a convenient recruiting ground for Zero/Precht.