According to Jia Yi's On Qin, didn't Qin Xiaogong annex six countries? Why are you still talking about Qin Shihuang unifying the six countries?

The reform of filial piety and business king enriched the state of Qin and enhanced its strength. Later generations of Qin kings constantly increased the territory and strength of Qin State. For example, Qin Huiwen captured Shu to the south; Qin Wuwang takes Yiyang, the military center of East Korea and the gateway of Luoyang, the capital of Zhou Dynasty; The king of Qin defeated 400,000 elites of Zhao State and established Ying, the capital of Chu State. The previous generations of Qin kings weakened the strength of the six countries and strengthened the strength of Qin itself. Finally, Qin Shihuang unified the six countries. "Qin Dynasty" wrote: Since there is no filial piety, Huiwen, Wuwu and Zhao Xiang don't know the past. Because of its legacy, Hanzhong in the south, Ba and Shu in the west, fertile land in the east and key counties in the north. Then there is: when the first emperor Fen VI was brave, he conquered the internal affairs with a long-term strategy, swallowed the princes who died two weeks ago, and made Liuhe under the supreme rule, beating and flogging the world, which was famous all over the world.