How can I report someone I HAVEN'T played with?

Long story short, someone in champ select was talking about how they're going to int this game. Didn't give a reason why. Thought they were kidding but went to their OP.GG to find that they're on a 7 game loss/int streak (their KDA in all of these losses are 0/10/0 or worse) and I decided to dodge rather than play it out because I didn't really want to get tilted my first game of the day.

I took a screencap of him admitting he was going to int and went to report him, but unfortunately I'm getting an error saying that I need to play with someone in order to report them... What? So I can't report somebody blatantly saying they're going to int the game until I play through a game with them and have them int a game with me in it??

Is there a way around this or are champ select hostages not reportable anymore?