My take on your comment.
Accepting the premise of: "you have both credibly committed"(a nice phrase) -> removes reason to be suspicious.
Removing suspicion -> removes fear. Removing fear -> removes anxiety/anger. Less suspicion, fear, anxiety and anger -> Less effort
Hence: "Committing to make it work makes it easier to make it work." (another nice phrase)
On the one hand you are committing to work. Who wants to sign up for more of that!? On the other hand, it really does reduce the overall workload. Long term relationships may be less scary than people realise.
When my wife does something that irritates me, my first question is "What error in communication led to our team play resulting in this?", because I have already accepted she is not doing it from spite.
Finding out what you don't want is definitely important too. Some people figure that out quickly, some go through a lot of drama before they finally figure it out. And I can certainly see how people who have trouble figuring out what they don't want, may enter a marriage that doesn't work out. But I also think that people who marry with relatively little dating, are more committed to making it work.