I wouldn't be surprised if this was some sort of PR campaign similar to Iraq's WMDs. It does make sense that Iraq still has weapons of mass destruction and could use them against civil populations; likewise, it does make sense that China could access the supply chain, and could use it to access government and corporate networks. The end goal is to change public perception and get support on the idea that the US should focus its efforts on that country (instead of the Mueller investigation or Russia for example). In Iraq's WMDs, the symbol was Colin Powell's vial of Anthrax, here it's a tiny chip that promises to unlock all servers. It's a symbol strong enough that goes well on TV or media.

True or not, what matters is that the seeds of distrust has been sowed. It's billions of $ lost for Supermicro shareholders, and potentially distrust of China.