Well, it means that provision for the second flash was already there, and PLA simply exploited that fact that Aspeed chips are virtually omnipresent in higher end servers.

It also means that the extend of intervention into board design was minimal, and that a trivial automatic xray would not have picked it up. And as implied in the article, later they buried the bug to beat the AOI, if it was done higher upstream.

So, they would've been screwed even if they were doing board testing outside of China.

That's a clever trick.

But the sole fact that the chip has "to phone home" makes detection trivial, and puts the usefulness of the method to nil - anybody sees the router blink when it shouldn't and your bug's cover is blown.