Damn, some people really have hate-boners for usually perfect characters making a mistake. Hak was getting boring with how long it's been since he's lost, and he probably wasn't immediately killed because they wanted to confirm he was convinced of Soo-Won's illness and he hadn't jumped to a wrong conclusion. Advisor guy wants to kill him, but can't without good reason, and confirming him knowing was a good enough reason until Yona came in and said "It ain't".
As for "Why didn't Yona say blah blah blah": page limit. Sensei wanting to end the chapter with a kiss. Not wanting Hak to go into stupid rage-mode when he's gravely injured. Not wanting to discuss the history in detail with anyone before clarifying with Soo-Won what is only assumptions on his mother's and her parts.
TL getting salty that Soo-Won isn't a boring 2D villain and instead complex and Our Heroes have weaknesses. AnY isn't some shounen isekai where the hero's always perfect and the villain laughs evilly because they're evil.