The projection that Pei Xuanjing had solidified from the foundation of his Great Tao wasn't created out of thin air but was bound to emerge.
The harmonious progress in the refinement of essence, qi, and spirit indicated that there was no deficiency in Pei Xuanjing's cultivation path – it was perfect.
This is why he manifested the projection symbolizing the foundation of the Great Tao.
However, for the Red Sun Martial Venerate, his situation was different because of his background in this world. The primary method he cultivated was the Path of Qi Refinement, which he had pursued to the extreme, being only half a step away from entering the celestial realm. His current realm undoubtedly proved his innate talent and comprehension to be unmatched.
However, he was not truly cultivating all three methods simultaneously. The farther he journeyed down the Path of Qi Refinement, the more evident his deficiency became. His gap in refining the essence and spirit became larger.