If you use AI to write the documentation, then it's unlikely to be better than the documentation people could generate themselves with GPT-4. But it will be a while before it's better than documentation written by professional writers that have all the context, target audience in mind and know what they are documentation inside and out.
The big advantage of doing it ahead of time is that you can proofread and edit it. LLMs are good, but it'll be a while before they get to a point where a bit of human editing doesn't help.