Supreme beings rarely admit their mistakes.
Heavenly King Yuan Shi and Sect Leader Tongtian made so many mistakes during the Fated Calamity, but until the calamity ended and the Three Sects were almost entirely annihilated, neither Heavenly King Yuan Shi nor Sect Leader Tongtian bowed their heads to admit their wrongs.
That's because admitting fault is truly difficult, especially for supreme beings.
The fact that Heavenly King Yuan Shi can now confront his own vanity and past faults proves that his mindset has completely transcended his state of mind during the Fated Calamity.
As a Saint's state of mind ascends, typically their cultivation base stage advances as well.