Nourishing Spirit involves nurturing not the Primordial Spirit, but Divine Abilities.
Body Refining Martial Arts does not focus on the Primordial Spirit. Rather, Body Refining Martial Arts relies on strengthening the physical body to nourish the Primordial Spirit, ultimately, the foundation for the Primordial Spirit's enhancement is the body itself.
Of course, this might also relate to Body Refining Martial Arts not valuing Comprehension heavily, as practitioners of Body Refining are often labeled as brute warriors, while cultivating the Primordial Spirit is delicate and requires Comprehension.
"Add Scripture of the Three Emperors!"
Wei Fan quickly gathered his thoughts, and his interface started to shimmer.
Inside his Sea of Consciousness, the Primordial Spirit's three eyes opened simultaneously, emitting golden light, with the Divine Ring bright and intertwining behind it.
