Your whole paragraph contradicts itself. At first you said Jumin isn’t dumb enough to admit it and that it’s poor writing, yet you use that same scenario to explain why he admitted it and how it proves he’s a mastermind therefore "smart". At this point, it feels like you’ll say anything as long as it supports your point or what you call “logic and consistency.”
The MAIN reason Jumin did what he did was because he feels inferior to Jaekyung — jealousy, disdain, insecurity. His primary goal was never the championship; it was Jaekyung’s downfall, how can I define someone like that as smart? He’s cunning and manipulative but that’s not the same as being "smart".
And realistically based on your “logic and consistency”, if Jumin is actually as "smart" as you claim, he’d probably have the pervy mf k-illed or bribe the police before getting caught anyway, which makes the interrogation scenario even poorer writing.
Let's say a police investigation and interrogation happened, Jaekyung would never have found out it was Jumin before the fight because realistically they take time. In his mental state, he probably would’ve lost. Then what? How would the story move forward at the final major arc?
The only thing Jumin achieved with his “single sentence” was getting brutally punched by Jaekyung😂. He couldn’t even land a single punch. Quite Pathetic.
You can write your own story too — let’s see how “logical” and “consistent” it turns out.
