User blog comment:Miskos3/Fairy Tail 522 & 523: Gray's Trump Card & Is Destiny Burning, Review/@comment-26389992-20170222015906/@comment-26389992-20170222120113

Yeah Misk this girl on tumblr named Sarapyon said it was mistranslated. "Last arc" is supposed to be "final chapter/section" which could be more referring to Alvarez being in it's "final section". Plus people say that the Magazine or the Author themselves is who confirms a manga is in its final arc.