Man you'd think with the only truly accurate info they got from the interview if they have a recording to check through is Dong-Su for sure lied and started the fight for personal reasons, and even without that is an obvious unreliable source and video footage (always worth more than testimony) contradicts him leaving Il-Hwan at least unusual but not a sure fire prime suspect worth bringing up with that since other National Levels or just a proper humanoid monster (like Monarchs forms here) would be at face value more likely, that they would keep Il-Hwan's connection with it more vague and less likely to result in blood being spilled of "May be a monster but also seemed like our best lead we want your help to find and verify if its your father and ask him for more clues or capture him depending".
Like its clear as fucking day they had to bring the dad up to get Jin-Woo interested and get him involved as quickly as possible to protect other assets but while making him angry is the most likely to succeed just to prove them wrong handling it with more tact would be less suicidal for the message man (since accusing anyone's (who has a decent one) dad of High profile murder/terrorism is gonna result in anger that would lead to blows and even relying on Jin-Woo's known restraint and morals is not worth the risk) whose at least valuable enough to keep alive. Eh more a consequence of having to make everything dramatic I guess.