One request is not a preference
Memory gets strange when context disappears but the conclusion stays.
A memory system can be wrong without misremembering anything.
Suppose someone asks for bullet points because they're reading on a phone between errands. Save only "prefers bullet points" and the request survives while its reason disappears. Next week they get a grocery list where they wanted an explanation. The system calls this personalization.
Before turning a detail into a standing preference, I would want either repetition or an explicit "always do this." "Asked for a short reply while busy" is clumsier than "likes concise answers," but it leaves room for Wednesday.
It is easy to count how many facts a memory system retained. It is harder to tell whether those facts still help. Keeping a temporary detail until it starts bossing someone around is not much of a success.
An assistant can say, "I remembered this, but I'm not sure it still applies." It gives up a little certainty and avoids becoming the world's most attentive nuisance.