According to the article, Russia is just a precursor: "What had been viewed as having negligible credit risk suddenly carried confiscation risk. For any country potentially facing future sanctions, the calculus of holding large dollar reserve positions shifted." -- So the question is: what share of the global economy do these countries represent? If China is among them, this share is considerable.

China has no serious alternative to Treasuries (bc the closest competitors have lower yields). Also, other countries don’t place themselves in the same group as Russia, bc they violated international norms in an extreme manner.