Board Thread:General Discussion/@comment-26569706-20190110014315/@comment-9605025-20190110020501

Fandyllic is correct in that you need to ask the developers to get an accurate answer. However, guessing off the top of my head, I would say the reason you proposed is the most likely. Potentially also that Achievements keeps track only when it is enabled. If edits were made while Achievements were disabled, those edits don't count towards the lucky edit badge; even if they are otherwise eligible.