My mother did this; started when I was very little, so too young for it to be linked to any age-related issues.

Based on the tone of voice she would use and her particular patterns, I found it could due to a few things:

1) She’s playing stupid and trying to steer the conversation to something on her agenda.

2) She’s highlighting her favorite issue - how distant we are. She knows nothing about me! I tell her nothing! Or else clearly she would know these basic things about my life (that she does, in fact know).

3) She’s trying to get me to talk/chatter. I was a quiet kid, and her chosen tactic was to pepper me with lots and lots of questions. This continued into adulthood, and I found she often warmed up by asking questions that she already knew. (Also - possibly testing me/seeing if I’m being consistent/“honest” with her)

4) She is mad at me and wants to make it clear that she has better things to do than to retain knowledge on my worthless little existence. Typical passive evil aggressive behavior where she shames/degrades/makes others feel insignificant.

It’s part of what made it so difficult to orient with my mother - the “why” shifted constantly, yet the poor behaviors were persistent. I hear you that it’s super frustrating and confusing.