It's quite likely that continuing to practice the "Purifying World Lotus" requires not the growth of the physique, but rather lacks some critical prop or medicine.
The methods of the Demonic Sect cannot be that simple.
No matter how much kindness and severity are applied, betrayal is inevitable...
Therefore, they must have some methods to control the Dharma Protector Deity General.
Or rather, to make them not dare to betray.
The most reasonable explanation is:
'I haven't learned all of this cultivation technique, or I'm missing some critical aspect.'
'This, Tang Lin'er probably doesn't know; he's still circulating at the First Level, completely unaware of what the subsequent bottleneck might look like.'
With this thought in mind, Zhou Ping'an didn't dwell on it; his current priority was to expand his achievements.