User blog comment:Miskos3/Fairy Tail 527: Emotion, Review/@comment-24489996-20170318131937/@comment-2214433-20170318141813

Perhaps I should be more specific: when I say 'pulling stuff outta his ass', it's really just another term for what the translation calls 'recent made-ups'. The thing is, in many cases, when it comes to serialized work, it's just impossible to have everything planned, these authors don't have the luxury of book writers who can go back and correct things in early chapters so that the story flows well. Even authors such as Attack on Titan's Isayama, who've made statements about having their story heavily planned in advance, admitted that as the story went on, they simply ended up making minor to major changes; it's literally what Mashima says in his afterword.

So sometimes, in this kind of 'literature', the author indeed must have a talent to hide that he's just made something up on spot, something he may not have wanted to do before the arc started, and so on. Sure, this kind of writing isn't good per se, but if the author manages to come up with something new and integrates it into the story so that it flows well with it, isn't that a good thing in the long run? Or the very least, better than having to rely on literal retcons.