Tell me the logic behind this. From where you get this idea?
In all the instances we've seen the Yang Healing been used, its never once stopped the effects of Ninjutsu nor reversed them. It has stopped the effects of physical trauma caused to the body or life force and it has reversed physical trauma caused to the body. There is nothing to even imply that it can reverse or affect Ninjutsu or chakra specifically. Not to mention that it is a "Yang" power, which fits into the realm of the physical and not the spiritual like Yin Chakra.
In Gai's case, the Ninjutsu effect was to cause physical trauma in the sense that it would (apparently) heat the body to such a degree that it would turn to ash. The Yang Seal was able to reverse this effect by treating the physical trauma caused by the chakra. It doesn't stop the chakra, nor reverse its effects. It reversed the effects caused to the physical body by the chakra. Chakra is two parts, one physical and one spiritual, Yin and Yang, stamina and soul as explained by Ebisu in Part 1.
In order to save Gai two things where required. Cure the physical trauma, as in the intense heat inside the body and to recharge the heart's life force that binds the soul to the body. It successfully did these things and thus saved Gai.
In Kakashi's example, what the Yang Seal was required to do was to fix the physical trauma caused by him having his original eye removed. It did this by effectively forcing the cells in Kakashi's body to work on overdrive to grow a new eye, using the other eye a blueprint. This is well within both the realm of real life science and the Narutoverse as this is how Naruto for example if able to heal injuries as Kurama's Yang Chakra is so intense that it forces his cells to work on overdrive to heal.
In Obito's original case he was already dead, his soul was leaving his body. However, Naruto used the Yang Seal to tie his body and soul together for a limited time again. This is (as stated earlier) implied by their dialogue.
In the Ash Bone example things are different. In order to cure and stop this attack a few things has to happen. For one the person healing it has to stop the chakra from the Ash Bones to spread, not just cure the physical trauma as the Jutsu is still in effect unlike with Gai where the Jutsu had ended. In order to stop this chakra, the user would need to find all traces of it and blow it out like a flame. In Gai's case it was his own chakra working against him, and the fix to that was to forcefully reverse the effects of the Yang chakra in his body that was destroying his body, as is the powers of the Yang Seal.
In Obito's case, Naruto was neither fast enough nor aware enough of the Ash Bone technique in order to stop it in time. Even if he could do that there would be other things required to save Obito's life. For one he would need to heal the body by forcing his cells to replicate quickly, which we saw earlier that it takes time and unlike Gai there wasn't an internal source to reverse, but it required external force like with Kakashi's eye. Along with all of this, Naruto would also need to tie down Obito's lifeforce which was leaving his body. Which likely wouldn't work very well as he had already demonstrated the inability to do so as Obito was technically dead.
