Wu Qi simply couldn't understand Steamed Bun's actions. However, for the viewers, Steamed Bun ignoring Wu Qi was actually quite logical.
His Steamed Bun Invasion had been positioned close to where Soft Mist was killed. Cloud Piercer and Empty Waves could easily switch targets to Steamed Bun Invasion and form a pincer. Along with support from Wu Qi's Cruel Silence, even if they failed to kill Steamed Bun Invasion in one go, they would certainly be able to injure him severely.
Steamed Bun was quite quick to catch on, and Steamed Bun Invasion quickly left his original position. But still, throwing out an attack at Cruel Silence wouldn't have delayed his retreat much. Throwing out an attack would have slowed down Cruel Silence's pursuit as well.
Steamed Bun hadn't attacked, but it didn't hinder him in any way. By doing nothing, he actually confused Wu Qi. In fact, compared to throwing out a skill, this confusion hindered Wu Qi more.