Well, if that the case then the 7th level was not really exist. 1st, because the creator was only imagine it, and never know if his theory was right or not. If Zhang Wuji managed to reach that level, then it was Zhang Wu Ji who created that level. But if Zhang Wuji was even failed to master it, then it was not Wuji's fault. But because the creator theory was wrong, and didn't work in reality.
Think about it. If you can create a high level martial art like Qian Kun shift with only imagine it, and never practice it, then even Wang Yuyan can create an ultimate martial art with only imagine it with her mind. As she possess a lot of martial art theory, but never practice any of them.
Well like I said before you need "supermassive internal energy" to fully mastered Qian Kun Shift and since no one from Ming Cult ever reach Wuji's level of internal strength so it's almost impossible for them to mastered Qian Kun Shift until highest level like Wuji not even the creator..
...which kind of reinforces the idea that 9 Yum Jen Ging, if mastered, should be an effective counter to Keen Kwun Dai Loi Yee. In its time, 9 Yum Jen Ging seemed to be an effective counter to just about everything, as it was overall superior to the Greats' native skills.
As a better skills yes but what I mean 9 Yin is not "direct counter" for Qian Kun Shift since in L/ROCH JY never say anything about Qian Kun Shift even Wuji after learn 9 Yin also never say anything about Qian Kun Shift and how to counter it which indicate 9 Yin is not designated to counter Qian Kun Shift..
When Chow Bak Tung told Gwok Jing about the origins of the 9 Yum Jen Ging (LOCH), Chow said that Wong Seung created the second part of the 9 Yum Jen Ging specifically to deal with the wide array of martial arts that associates of the Ming Cult practiced. It likely also included methods that would be effective against the Keen Kwun Dai Loi Yee as that was the best martial art associated with the Ming Cult and Wong likely anticipated a confrontation with the Ming Cult Leader.