This adaptation is such a bastardization of the source material. CXZ allowing LMT's grandfather to beat him out of remorse makes sense in the novel because, although CXZ helped and protected LMT, he also took her virginity. So, CXZ's grave mistake wasn't simply that he lied. In this drama, CXZ did nothing nefarious. He lied at first because he thought LMT was the enemy's concubine. He continued lying because he fell in love with LMT and didn't want to lose her. So, in drama, he saved her, nurtured her back to health, protected her, and didn't sleep with her when he had the chance. Yet, the drama version of CXZ is treated like he committed some grave crime.
The drama suggests that LMT could live her life single, childless, and happy indefinitely. This is rarely true even in modern times. However, the novel takes a more realistic approach by illustrating the challenges a beautiful, unmarried woman would face during that time. Not every powerful man was as kind as CXZ. In the novel, there was balance. LMT needed CXZ as much as CXZ needed her.
Excerpt from the novel:
"What Liu Mian Tang wanted was never mountains of gold and silver or dominion over the land. She desired a person who truly loved her, who would stand by her side and give her the trust that comes with standing back-to-back."
However, the drama conveys a different message: LMT doesn’t need a man to find happiness—she's perfectly capable on her own (In reality, she's not). CXZ is fortunate that she’s even considering taking him back.