A deleted tweet always appears in Unified Moderation after it is pulled into a feed. Social does not do anything to update deleted tweets in the feeds.
If a tweet is deleted from Twitter before it gets pulled into a feed, then it will never appear in the feed. If a tweet is deleted from Twitter after the tweet displays in the Social feed, it remains in the feed.
There is no way to know that a tweet in the moderation feed was deleted until you try to Like or Reply to it in the feed. Then, a failed moderation action message appears, indicating the post is no longer available.