Why can't Qin's official position be Qin? Because the monarch of the State of Qin is the descendant of the concubine, and the concubine is Zhao, although some people very much hope that he can be changed to the State of Qin, they can't produce any historical evidence except imagination and obscenity.
After the concubine was sealed to Qin, do you want to change the family of Qin? The answer is obviously not yes. Because many vassals or monarchs didn't change their surnames after being blocked, if the illegitimate child of a small vassal is qualified to change his surnames, it is that Lu Shang (Qi Taigong, the legendary Jiang Ziya) is more qualified to change his surnames. Lu Shang was a first-class minister in terms of credit, rank and fief area, but he didn't call himself "Shang Qi". In addition, the strength of the monarch of Chu is far beyond Fei Zi. According to the research results of pseudo-scholars, the king of Chu can also call himself "Chu Moumou", but the fact is very embarrassing. They have always been "Xiong Moumou".
In fact, not only the monarchs of Qi and Chu have not changed their names, but also the monarchs of Yan, Lu, Jin and Wei have not changed their names to "Yan surnamed Ji" and "Lu surnamed Ji" ... because, under normal circumstances, this kind of thing will only happen after the national subjugation, that is to say, the word "Lu", for example, was taken as the surname by the people who lost their country after the death of Lu. Qi mentioned earlier also has the same example. Today, some surnames of Qi began after being usurped, and there are surnames such as Chen, Cai, Yan, Jin and Liang. The word "Qin" is no exception. It was only after the national subjugation of the Qin Dynasty that it was taken as the surname by some adherents of the Qin State. In this case, do Qin and the monarchs of the Qin Dynasty still want to call themselves "Qin Moumou"?