User blog comment:FairyRaven/Fairy Tail Chapter 423: Do It All for Love, Review and Commentary/@comment-87.202.75.211-20150309114538/@comment-9595671-20150315014800

Well from what I've heard had the group trained for 3 months they would have unlocked without realizing, but Mashima wanted to hurry and get to the games so he created a faster way through Ultear's magic.

I mean it is plausible, it is a power based on one's magic container capacity. And if research found out about it while Ultear's magic is something only she knows how to use due to being Lost Magic, it makes sense from what I can see that you can naturally unlock it through training.