User blog comment:FairyRaven/Fairy Tail Chapter 465: 400 Years, Review and Commentary/@comment-27281341-20151207194925/@comment-9595671-20151207200938

It's also possible the only part about Natsu being END is giving Natsu back life, he might not have any curse power.

The chapter for one implies he wanted Igneel to make him a DS, the other demons learned curses in the 400 years after.

Natsu might not know curses cause when he went to the future, they hadn't been created just yet.