OpenAI needs to IPO because they want to access the public capital markets to fund their AI investments, more deep-pocketed investors are wary of investing in a LLC, and for liquidity, etc.

OpenAI needs to convert to a C-corp in order to IPO.

OpenAI needs the CA Attorney General's approval to convert a LLC into a C-Corp because the LLCs is headquartered in CA and incorporated with many CA laws.

So the article is making the point that OpenAI likely got the CA Attorney General's approval for the conversion because they promised to stay in CA (whether or not that's actually true).

(or support journalism and pay to read the article)