There's a large misconception in a lot of the conjecture I see publicly, and it's the idea that China would care if it could be traced back to them. A lot of governments commit a large number of intel actions knowing they'll be traced back to them but it's still worth it. If they got caught they'd just say "Oh it's a rogue factory" and go one with life. Maybe we would throw some bullshit sanctions their way.

A historic example of this is the recording devices we used for Operation Ivy Bells. There was no hiding who the recording devices belonged to because we spray painted "Property of the US Government" on them. Or the Iran nuclear manufacturing tampering that was pulled off for years. Everyone knows who did it because who else could have done it?

Regarding 'scale' - that's not all that important either. If you have someone at SMCI that can get shipping orders then you can easily figure out roughly what batches you need to tamper with in order to make sure your parts end up where they need to go. And it's worth it, even in a small scale, on the hopes of not getting found. No one comes up with one idea of compromising a target and then never waivers from it. You try them all until one works.

I still believe though that China (and, in fact, the US itself) would have much more at stake if the US discovers that the supply chain has been compromised, given its enormous manufacturing interests and how this might be used to justify certain trading policies, whereas the US (and Israel) had, in comparison, almost nothing to worry about Stuxnet being traced back to them. This is the main reason I believe that if this was real it would have been incredibly rash from the Chinese, unbelievably so. Then again, it would also be extremely damaging to Bloomberg's reputation if it wasn't.