Like Madhuri said when she spoke to RK and Madhu (in the avatars at that time) that the chemistry comes with tension. So the war of words brings the tension, so that's partly what the article is talking about.
We all saw that the hate track is when we liked the chemistry between Rishbala. When the love track came we liked it sure but afterwards it became same all the time sweet romance hugging repeating the same scenes, however when they fight because the arguments are revolving different subjects and the characters also bring up different things to win the argument against the other, it becomes really good to watch. That part is what the article has dealt with.
But I think the CV's try to bring different emotions for the characters to feel for them to say the dialogues so we also feel what they are feeling and can relate so they don't have to be at loggerheads all the time, like when RK held Madhu in a hug and said Madhu you know you are my jaan and I'm only alive when you are with me, that dialogue is perfect example where we related to how he was feeling locked up in jail his clinging to only the love that he has with Madhu and when she is not with him he feels not himself, and now what is happening is he feels she is losing her mind and he wants to be with her to calm her and comfort her,here the tension has been provided by the problem they are having in their lives.
So I think the chemistry is brought by them having the right dialogues and expressions to suit the circumstances that we believe what they are showing us and can relate to what they are facing and saying whether they are fighting or consoling each other.
1