Is contradiction really contradiction?

Chu A boasted that he had the sharpest spear and the strongest shield in the world, while Chu B mocked that attacking your shield with your spear was even more powerful. Chu couldn't answer, and ran away despondently.

If the fact is that Chu 'a somehow refined the strongest substance in the world at that time, and his spear and shield were all refined with the same substance, then there is no better one. What he wants to express is that his spear can pierce any shield not made of this material, and his shield can stop any spear not made of this material. His spears and shields should be mass-produced for the benefit of Chu. However, what B, a native of Chu, said is not immortal, it has become an eternal joke. On the other hand, what benefits does Chu B, who thinks he is smart, get? His compatriots created disposable weapons. He didn't go to verify whether the spear and shield were really bad, but looked for the soft spot of Chu A's speech and tried to be quick-tongued, but he didn't know whether it was Qin Chu or Qin Chu.

Then, if the contradiction itself is not contradictory, where does the contradiction come from?