Microsoft AA round

I had my AA round recently for SDE1 role which was my 3rd and last interview for the loop (idk why as they generally have 4, but first 2 rounds went pretty good)
it was just a very casual conversation for first 10 minutes. After which he gave me an algorithmic problem (literally typed in the chat section). I discussed a generic approach, but he wanted me to code it even though I told him that I wanted to spend some time to go through my approach, so I coded it and obviously there were some holes in the approach which he pointed and I corrected them without any help.
He closed the interview in about 45 min even though it was scheduled for 1 hour plus he didn’t really ask any behavioural questions or past experience.
Can anyone please tell me or provide me some feedback what made him close the interview early and not ask me any other questions?