Yes, Liverpool were the better team for most of the match (albeit the whole first half was drab), but that doesn't always guarantee points and Man U could have snatched a win at the end.
I think the point it, Liverpool did underperform in comparison to most of the rest of the season.
I think people are getting a little hyped on United's performance. The XG was 2.97 to 0.99 in Liverpool's favour.