User blog comment:Kaido King of the Beasts/Chapter 904: The Revolution Will Not Be on the Loudspeaker/@comment-25654036-20180512111738/@comment-25501246-20180513022703

There's nothing to address here.

Morley is a Giant, with 3 different characters (including his teammate) referring to him as such. There's no rule that Giants can't have Devil Fruit powers.