Here on Meta I have the ai tag muted (I simply don’t want to see it) and my notification preferences for Announcements is set to watching first post so I get notified for new posts, which works as intended, but posts tagged ai are not excluded from emails or user notifications.
That was about a different topic and in the end we found out that while the topic was now in a category that wasn’t watched it had been in one before which caused the notification.
Can you still look at the checkbox in your preferences? Otherwise, we won’t know whether it’s expected that you are notified because we cannot say if watching Announcements or muting ai is supposed to win.
Sometimes it’s a little difficult to find the checkbox, but you can enter something into the category watching field if it’s not visible otherwise.