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.
Not every part of your ideas need to be novel and unadulterated by the rest of human progress. If your ideas need to fit in to some wider context (e.g. you need to produce working code) then it is very helpful to be able to look up important facts about that wider context rather than guessing.
If looking up helps you catch a misconception or missunderstanding about the real world, it's great.
I find it very hard for external sources to support my thinking (if they do I don't read them but save for later comparison). If anything they prove me wrong when I am on the wrong path.
I have had ideas that come to me, during walks, and other certain moments, briefly and they keep developing over time. It has happened that after I actually write them down, my mind stops caring about them and they stop happening.
Alternatively I have had ideas in mind that get stronger and stronger and at some point I just have to work them and so I work on them without writing them down and I actually bring them to fruition while writing down might have oddly killed that motivation or obsession.
It is mainly various side projects. The act of writing somehow diminishes that motivation or reward feeling as opposed to immediately starting to build the side project.
I've had many ideas that have been watered down by the editing process that by the time I'm done have lost the impact or connection to the original idea.
Maybe I lack the vocabulary? Writing skills? Maybe I'm self censoring? Maybe it's my perfectionism optimising the local maxima?
I don't know but I do know writing has ruined some, not all, of my ideas.
This also wasn't my main issue above. I was more concerned that the idea you can't have good ideas without writing them down was deeply flawed and a bit gatekeepery.
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.