No, the imaginary Yujiro is causing the effect. It’s not new, we literally see Baki’s imaginary fighters physically affect the world in a way that would make it impossible for Baki to have done anything, such as when Baki fought the imaginary Retsu and Retsu beat him so badly, he bleed out all over the locker room. We also see this during the fight, with Baki being hit by nothing and Baki’s hand literally just slicing open. We see this again in Baki’s Prey Mantis fight. Baki’s imagination has been seen to affect his environment before. Besides, even if it were just Baki throwing himself against the wall, he still couldn’t even imagine Pickle’s body, implying that while a weak base Yujiro could be 8-B, 8-B wouldn’t even compare to a weak base Pickle according to Baki.