Learning that Senior Xukong knew of Body cultivation techniques was a huge relief for Lin Mu.
Back in the Xiaofan world, Xukong couldn't really teach him any due to the fact that none of the techniques he had were suitable for Lin Mu's cultivation base, nor the world that he was in.
All of them were at the immortal realm at the minimum, with the Mortal Strengthening Scripture being the only one that could be considered as the lowest technique. But even then, the Mortal Strengthening Scripture wasn't a complete body cultivation technique.
Rather, it was meant to be a defensive technique that just happened to have a passive effect of strengthening one's body.
But now Lin Mu could fully utilize the techniques that Xukong knew.
Qi cultivation techniques were not something that Lin Mu needed since he was cultivating his own method, taking the primordial path. But he still needed the body cultivating techniques to progress further.