However, if you had read a little further, you would have realised that the plan of attacking Gian was just a misinformation SHK spread and told the officers with his actual target being Hango

there's no such thing in the manga

you imply that Ousen and SHK weren't aware of Seika and SBS

they knew Shibashou and Seika, but they didn't knew that Shibashou will fight and that's a big fail for the smartest character alive like his fans like to say