现在分词做状语，它的逻辑主语理论上是主句的主语，但是，这个怎么解释呢？

Question

That has led some customers to take to social media, saying they can no longer afford to buy the vegetable, which is known as xiangchun in Chinese.
答案的解析的saying的逻辑主语是customers，但是一般逻辑主语应该是that，这个又怎么解释呢？