The Divine Realm was a different beast compared to the other major realms. The Body Refining through the Sky Realm was essentially refinement. Improve the quality of Qi, the body, and soul if necessary.
Even with tribulations and physiques, that was essentially true.
The Heaven Realm was about expanding the elements. The missing pieces had to be filled in and then once more refined but also improved understanding of how all 6 elements interact.
Essentially still refinement but also touching on higher order relationships to advance from the Star to the Sun Tier.
The Immortal Realm seemed like a bastard after that. A massive increase in lifespan but that was because refinement was no longer the main goal. Laws had to be grasped and incorporated into a transformed dantian.
The first 3 tiers from Sliver to Crystal were just that. The Radiant and Sovereign Tiers were massive steps forward. Not only grasping Laws but to begin touching on the Dao to advance.
