Well, there's nothing in this article that would suggest that... This article confirms such attacks have happened already:

"Totally possible. We have been a witness, or have been involved in an investigation, not in the US by the way, but who cares. Eventually, the one who switched the box was a guy who got money to switch boxes during the shipment."

The only thing Yossi want's to clarify is that it's not specific to SuperMicro, and that therefore it's a much bigger and worse problem than if it was.