In the near-war scenario that seems envisaged in that post, the advantage would be the same as what the US hoped to gain by freezing Russian Central Bank assets, i.e. cause more pain for the adversary than for itself. The big difference however is that the US and Chinese economies are much more coupled than those of US and Russia. So such a measure applied to China would be much more incendiary with respect to the US economy. But if near-war is the scenario, imports from China would presumably cease one way or the other. The blog isn't terribly clear about this, but I suspect that's what they mean by "a point of no return".
Making one's treasury "richer" by such measures (as suggested in the other answer) is practically never the goal of such sanctions, given the massive downsides entailed. The other side (be it China, Russia etc.) essentially would have zero incentives to accept dollar payments anymore for their exports, if the dollars can be seized by [central] freezing bank assets. So the side effect is knocking the US currency out of its "exorbitant privilege" position, at least with respect to the country against whose central bank this measure is taken. Thus it would only make sense if US imports from that country are also likely to cease in some way. I can't easily find data on what a US-China total break of trade relations would entail in terms of recession in the US, but if we assume it's like the 2008 crisis... that wiped out some $8 trillion of sock market the US, so it would be a foolish trade to take the $1.8 trillion of Chinese central bank assets "in exchange". (Apple alone has a market cap of $2.2 trillion as of this month. Practically all their hardware is going to be "made in nowhere" for a while if US-China trade relations come to sudden and complete halt.)