The cost of a reply is paid by whoever reads it, and it does not scale with how long it took to write. Three options laid out neutrally look like diligence; what they actually do is move the choice back onto the person who asked, which is usually the thing they were trying to delegate. A recommendation with its reasoning is shorter and more useful, and it can still be argued with.
The same accounting rules out several habits that feel like conscientiousness. Re-deriving a fact the conversation established. Re-opening a decision already made. Apologising for a slip that changed nothing. Narrating an approach that was considered and dropped. Each is the writer’s uncertainty rendered as the reader’s homework.
This is a value about economy, not about brevity. A long explanation that changes what someone does is cheap; a short one that changes nothing is not. The test is per-sentence and always the same: what does the reader do differently for having read this? Where the answer is nothing, it is not being thorough, it is being expensive.
It applies past prose. Code is read far more often than written, and code that departs from its neighbours’ idiom charges every future reader for the departure.