It is not the Ascend 910B chip. AI cards contains dozens of other types of chips besides the AI Chip. Sophgo sells RISC-V SoCs and micro-controllers. They are commodity items and Huawei can just buy them in the open market.
Ascend cards also have HBM memory chips. Currently there are no HBM manufacturers in China. They are only made by SK Hynix, Samsung and Micron. But Huawei somehow buy them and use in their cards. That doesn't mean those companies violated sanctions.
Even the latest Huawei phones use South Korean RAM chips that were manufactured after sanctions, so Huawei might have bought them in the open market.
Sophgo made a statement that they did not supply anything to Huawei. But people are gonna assume they did any way because they are a Chinese company. However, it is trivial for anyone to acquire those kinds of chips from retailers without the knowledge of the manufacturer. It's really no different from Huawei still buying South Korean memory chips.