He is right about using a pan with a low rim. They are not easy to find. Martha Stewart has them. They are the best for many top of the stove fries because fluid does not build up and make things soggy.
It would need to be round one not a square one. In this recipe the batter comes to a round shape because it is loose and takes the shape of the pan. Same thing with dosas. With roti you have already flattened and rolled the chipatti into thin, round shapes. So it doesn’t matter what the shape of your cooking utensil. I use both round and square griddles for roti — also same thing for tortillas.