It’s not actually about being specific per se - it’s about overtly mentioning details that are already assumed from context. Grice’s maxims of quantity and relevance say that speakers only provide information when that information is important in some way and relevant to the discussion, so providing information that would otherwise be assumed means that information must be actively relevant to the conversation in some important way that warrants it being mentioned.
Good on Magnus for sticking to his guns. The more I hear about that guy, the more I like him.