User blog comment:Lord Zeref Dragneel/Top 25 most powerful characters/@comment-25111584-20150812160455/@comment-3290324-20150813170239

As I've mentioned above, this is a shounen timeskip. Trying to apply real world logic to whether or not characters were training or not is pointless. :/ And you're right. There's no evidence... besides the fact Mashima provided stats for the Grand Magic Games participants and Erza, Mirajane, and Kagura all scored higher than Natsu, Gray, and Gajeel. :P