I understand that you are not asking for yourself and are bringing up a question. Here are my thoughts.
I know that there are people who rationalize things. They list the person's good attributes but in their heart they know they are settling. Do they realize that they are cheating the other person? They are keeping them from the chance of having a spouse who loves them. This is not right to do to them. They are also saying that when they take their vows, they are willing to lie. Neither of these things are part of Christian love. You need to care about the other person's needs. That other person,as well as themselves, will never have the real intimacy that most of us crave. They will have a sense of loss or emptiness because they are not their spouse's love.
I am not saying that love can't or doesn't grow within a relationship that didn't start out as romantic, but if someone has already decided that they do not have these feelings for someone, neither of you will end up happy.