Why is it that the exploits of the Yellow Emperor invented writing, and the history of writing can be tested is the beginning of the Shang Dynasty?

The Yellow Emperor is a legendary figure, and there is no archaeological evidence that the Yellow Emperor really exists. Moreover, whether the Yellow Emperor is a person or a title is inconclusive, so what you said is naturally a legend. According to legend, during the period of the Yellow Emperor, many things were invented, such as words, textiles, cars and compasses. Although these things were not invented by the Yellow Emperor, they were all invented during the period of the Yellow Emperor, and the Yellow Emperor played a major role in promoting them.

Historical characters can be verified from the Shang Dynasty, which is confirmed by archaeology. Although Oracle Bone Inscriptions is a very mature written language, we have reason to believe that our ancestors were able to use it before, but it has not been widely used because there is no evidence or the evidence is still controversial.

So, your problem is that you confuse legend with history.