This isn't the way I generally write, but sometimes I do this with the opening scene and go to drafts from there. As with draft writing, there are advantages to revising as you write.
1. Writing sentence by sentence can be liberating. Why.
Makes the daily sting look easy since one doesn't have to write the entire book,
It isn't a draft so revision has already been done when the end is reached.
One can always go back and tinker if a block occurs and doing this may solve the problem.
2. From the first page, the style tone, pace and viewpoint is established,
3. Lets the writer understand who the characters are.
4. Problems can be solved the moment the occur.
5. One can work out the next scene or solve the problem while not writing more than a sentence, paragraph or a scene at a time.
6. Allows the story to develop and be controlled. One may have to go back and expand a scene or cut a scene or words but the writer who revises as they go along doesn't have to go back and change what's already happened.