I'm just speculating here, but in a normal database you would have different processes writing the wal files to the database or archives.

You don't have that with sqlite, so I don't see an obvious advantage for this, except if they now spawn a process or thread to do this concurrently.

Edit: so I read the doc (shame on me) and it has nothing to do with speed. Its purpose is to prevent a wal file from growing too large.