I can't completely say but I think that it is likely that they are going through this for similar reasons that I am. Many, if not most, people have expectations about what their marriage is supposed to be, what a relationship is about, what they want from their partner...blah, blah, blah. This is almost never, ever discussed--love is "supposed" to make this kind of thing obvious, right? We wish.
I think for a lot of T-pref, love may be displayed in the form of action. For many women and for some men, they might start to feel like they are taken care of instead of being cared for. For myself, my cousin and my friend, it is a situation where the kind of love we display is not really seen as love but more like just doing our duty. Different types of displays are desired and preferable but resentment develops when these things have to be asked for. For example, he might be told that she really loves flowers. "Why don't you bring me flowers more often? I really love them. I wish you'd buy them for me more often." Next day, the flowers appear. He expects her to be happy--he did what he was asked to do, right? Wrong. She had to say something to him; it wasn't spontaneous, therefore not genuine. She pretends to be happy but is secretly angry that she had to tell him something that is obvious to her. He is upset because he can sense her unhappiness and wonders what the problem is. He did as she asked....
Or she may be angry about something. Sulks. Pouts. Goes to sleep on the couch. He asks if she's coming to bed. Reply is, "I'm sleeping here tonight." He says, "Okay--goodnight then." She wants him to draw her out..."what's wrong? Will you talk to me, please? I see you're upset." He figures that she wants to talk, then she will do so and he can't do anything until she speaks up. This also feels emotionally manipulative. She interprets this as him not caring about her feelings.
Multiply this by everyday and in just about every direction and you come to an endpoint.
I think this can be avoided by careful examination of the expectations each party has and how they will mutually meet them.