I wondered this too. Also "I'm bored" is a bit of an odd way to express wanting more affection. I don't blame Tristan for taking that the wrong way because being told someone is bored after you've organised stuff to do with them would sting. He still overreacted though. I wonder if their situation has been edited down quite a lot because to me the argument that we saw didn't quite match up with how they were describing it to the camera.
Part of me thinks they're both decent people but, like Lucinda and Tim, totally mismatched in key things like how they handle conflict, which is a bloody hard difference to overcome.