Looks to me like OpenAI drew their guardrails somewhere along a financial line. Generate a Micky Mouse or a Pikachu? Disney and Pokemon will sue the sh*t out of you. Ghibli? Probably not powerful enough to risk a multimillion years long court battle.
They did, but the rights expired. GKIDS now has the theatrical and home video rights to Studio Ghibli films in the US (except for Grave of the Fireflies).