Assuming the story is real it is quite obvious that there aren't that many compromised motherboards. It wouldn't make sense and it would make the attack easier to detect and to publicly incriminate the culprit.
As the attack is said to have been discovered 3 years ago it is also not surprising that housekeeping has already been done a long time ago.
As the attack is said to have been discovered 3 years ago it is also not surprising that housekeeping has already been done a long time ago.