I did send an update about 1 week after my interview, but it was just a brief note informing them of my GPA from Fall 2023 (it improved my overall GPA so I figured I'd send it in). In there I also included a short "thank you" message for interviewing me.
I haven't sent anything since then (5 weeks ago) and I figure I'll probably get my decision in the next 2 weeks (the portal says 8 weeks and I'm currently 6 weeks post-interview). I thought a letter of intent (or letter of continued interest or whatever) could help when that decision finally comes around, but wasn't sure if I should first wait to see if I get waitlisted.
Congrats on your A!
Edit: My LM is 69.5 if that matters? Looks like we have a similar profile haha