Short-form writing, by necessity, is an open form. When you’re done writing, there are many more points to be made, and more nuance to convey.
Statements are often made as absolutes, but absolutes cannot reflect the entirety of the argument (some frequent twitter users, aside, of course).
Long-form tends toward being closed. When you finish, all the arguments are made and there’s no more to add.
But are either really finished? Probably not.