Using Non-Phase Nameless Sword to bounce back the immortal technique, his Master's performance was really an eye opener for Wang Lu.
The Nameless Sword was a counterattack skill that rebounds the attack by withstanding the damage. In theory, any damage could be rebounded back as long as it was within one's own limit, but this was limited to the same level attacks. At the level of immortal technique, it was difficult to say whether Non-Phase Method could still work because the level difference was simply too high, far beyond the scope of understanding of Jindan Stage. And for an incomprehensible attack, the Nameless Sword would not even know how to begin to fight back.
Even for the number one Jindan in Nine Regions, understanding the immortal technique would be like a fantasy—even with Wang Wu's perception and intelligence, which were among the top standard in Nine Regions.