I don't know whether a wave of stoicism starts creeping up on you as you get older, but I've started noticing the same pattern in my mum. Because of the repeated "deadpan" expressions to many of exciting announcements in the past, I've completely stopped telling her stuff altogether as I can no longer take the stoic indifference and disinterest in parts of my life that don't concern her.
I won't open myself up to disappointment with blank emotionless responses anymore.
Thanks a lot for sharing. I could relate to everything you've narrated about your mum in this article.