I think better terms should be describing general expert/domain expert/company expert. I'll say it takes 3 to 18 months to become a domain expert at a company

I think better terms should be describing general expert/domain expert/company expert. I'll say it takes 3 to 18 months to become a domain expert at a company depending on the scope, if you are fresh out of school. Less if you already have relevant experience. And then years to become company/subject expert, and those you have to pay to keep them.