Yes, writing can be a productive focusing mechanism, it can also provide you with good reflections. But so can meditation, so can a good walk. It's a tool, not a requirement. It also has it's own downsides in that it forces you to think a certain constrained way, and while that is also one of its strength, it does limit your ability to think creatively.
Similar to how using ChatGPt to draft writing or code, there is a strong biasing effect pushing you towards something non novel.