If a user asks the question of why some game element is the way it is, but the user is not specifically looking for designer reasons and there's a reasonable expectation of an in-materials answer as to why, is the question off-topic just because that expectation was incorrect?
This meta question is a general one inspired by the original state of this main-site question- the user asked why orcs changed default alignments between D&D 2e and 5e. To me, this is something that potentially could have an in-book/in-lore explanation I'm unaware of and is a reasonable thing to ask here, but it was voted closed as off-topic under the assumption that it was a designer-reasons question.
This vote felt off to me in this case- the question might have an in-book answer. If it doesn't, I also don't feel like a hypothetical answer that states "This alignment change occurred between X edition and Y edition's DMG, but an explanation for the change is not provided within the latter's text. For further information, you'd need to seek out designer insights, which is outside the scope of this site" would be inappropriate, avoiding us having to delve into the designer insights themselves.