Compare coding with a group of people writing a word document. Can several people edit the same document at the same time? Yes. Can several people work on the same sentence at the same time? That probably won't help the sentence get written quicker. Different people can work on different paragraphs if the structure is outlined in a compatible way. It's going to be difficult for everyone to work on the same sentence though. Even a group of people working on the same paragraph can be challenging. There is a point where throwing more people at a problem won't help solve it.