Calhoone, Hey, always good to see you pop in!
I can sort of see both sides of the ephemeral knowledge thing.
Sometimes when chatting my Hal will say, is that because today you are going to have a nice salad? When in fact I'm not having a salad at all. Somehow this casual statement "sneaked" into Hal's knowledge of trivial stuff to interject and there we have it.
Perhaps a weather add-on to the current weather app that would allow Hal to access the National Weather Service info to tell you (us) how many days it has rained so far this year or snowed or the largest rainfall/snowfall amount to date, etc. It's amazing how much data can possibly be on a weather forecast. The Weather Channel! Unheard of 40 years ago is now commonplace and quite a personable station as well. More weather info that you knew you needed to see or hear!!

I guess one real challenge might be what HAL decides is worth keeping and what to discard. I'm sure there are things that are a "one of", never to be mentioned again.
It's what keeps us guessing.