Am I tripping but was he not aware that she's got the rep of being His Woman the entire time????
Realistically speaking I think it would take a lot more drawn out chapters to really follow the book to the letter, which the manhwa artist/studio might not afford, and the decision could have been made to deviate in order to keep up with that (and let's be real, the art really well done that it must be physically taxing to keep going for too long).
With the book I felt the delayed gratification of Riize's downfall where without the author's power the world around her slowly crumbled, whereas here we're seeing a more active effort of the world (and people like the Duke and Duchess) to unmask Riize's machinations and manipulations for what they are. I like that the Duke and Duchess are especially hard on Cliff and Riize for the damage they've dealt.
I feel like he made sure Ijin was able to visit their graves before he does something dangerous... Maybe he'll do something to join them and it might take a lot of people (like that other soldier who said that it was a shame his wife died in a mission) with him.