I'm 3C and my hair will look like that if I fine tooth comb and brush it (not recommended for overall hair health) and then braid it. I'm essentially taking out my curl pattern and putting in a wavy one.
I don't do it now, but I use to do it when I was a kid. Your hair does have to be loose enough to pull straight. It might not be possible without heat if you're 4B or 4C.