My only surprise here is the turn around. According to the people I listened to China was nowhere near the 7nm range, at all. Sanctions were put place no less than half a year ago, so for them to have figured it out this quickly is what's making it look sus. It takes nations years if not decades to get to thus point, and countries have failed trying too. My money is they are using western manufactured lithography equipment.
Edit: From the South China article:
TechInsights said SMIC used existing equipment and its second-generation 7-nm process to manufacture the 5G-capable Kirin 9000s for Huawei
Huawei was known to have been stockpiling chips from its HiSilicon unit before TSMC cut ties to comply with US sanctions