Gan Ning didn't realize that he had inadvertently discovered a path forward after Inner Qi Manifestation; alas, due to the issue of his realm, he missed out on it. Gan Ning never gave much thought to why the Kun Fish could use Inner Qi while being engulfed by Cloud Qi, which is an inconceivable feat for two forces that could nullify each other.
Imagine if Lyu Bu saw the unscientific feat of the Kun Fish and then decided to study the mutual conversion between Cloud Qi and Inner Qi. With his realm, it's highly possible he could figure it out after some time.
Think about it: if Lyu Bu could wield Inner Qi within Cloud Qi, tsk tsk tsk, probably not many people would be enough for him to kill single-handedly. Likewise, if he could use Inner Qi in a one-on-one battle, not even one Zhang Fei would suffice. Sadly, neither Chen Xi nor Gan Ning nor Taishi Ci understood the state of existence of that Kun Fish.