Hafs Qirat Not A Hijazi Script
If he means the language is not Quraishid, we have Qur’an which claims that it is revealed in the language of Quraish. The Quraishid did not object that it is no their dialect. No claim can be made without answering to the question and they Quraishid did not raise this objection or mentioned it. If he means script, then it evolved over the time.