I don't think that de Maistre's "quick answers" category is supposed to include answers based on sound expertise.

People are often confused about questions to which an expert in the relevant area will give a quick and reliably correct answer. However, an expert capable of answering a technical question competently is not someone who has "considered [the question] only briefly or not at all": he is in fact someone who has spent a great deal of time and effort (along with possessing the necessary talent) on understanding a broad class of questions that subsumes the one being asked.