Indeed, in this season Manchester United managed not to lose by Liverpool because after all, their first meeting this season was also in a Premier League match when Liverpool played at home, but Manchester United managed to hold Liverpool with a goalless draw because the final score was 0-0. Also, misfortune happened again to Liverpool against Manchester United in the FA Cup because Liverpool lost the match.
But for me, even though Liverpool was eliminated in the FA Cup but because match was played at Old Trafford then yes, it's natural that Liverpool lost. But anyway, Liverpool is also really not easy to beat even though Liverpool doesn't play all its key players in that match. But for their next meeting match in the Premier League match later even though it will be played at Old Trafford too, I personally still believe that Liverpool are still able not to lose because I am sure Liverpool will beat Manchester United at Old Trafford later.
I also think the same as you that even though Liverpool lost in the FA Cup, that doesn't mean Liverpool will also lose to Manchester United in the Premier League. In fact, I am quite sure that Manchester United will not be able to beat Liverpool in the Premier League. It's just quite unfortunate. Because while many people are starting to expect Klopp to get lots of trophies this season with Liverpool, Liverpool are actually starting to miss opportunities one by one to win trophies. Now only the Premier League and European League remain. And I hope Klopp doesn't fail to bring his troops to lift the trophy on the two remaining occasions.