Likely due to the Black Dragon World's cultivation system having mental energy as its main focus, the Black Dragon World's 'heavenly tribulation' focused on attacking one's mind and consciousness, similar to an inner demon tribulation with some mental pain.
For ordinary cultivators, mental pain, which completely bypassed the defenses of one's physical body, was much worse than pain directed to their body in terms of pure suffering.
But for Song Shuhang... As long as the pain did not reach a point where it was a blow that could instantly obliterate him, he would be able to grit his teeth and endure.
Based on the Black Dragon World's heavenly tribulation of the Fifth Stage, he believed that he would be able to endure the Sixth Stage equivalent.
Of course, this was just an inference.
