So what you have in Jess and Luke are two people 50 times stronger than the average human. What you have in Matt and Danny are two highly trained yet still fragile and breakable humans. That's got to lead to some sexual issues. Especially when the first two don't know their own strength and the other two have been trained to be stoical and uncomplaining about pain. Bonus points if the bottom is unsure if the roughness is deliberate or not and the top is oblivious until they discover the injuries. Then horrified of course.