That’s exactly his point though. It’s more a reminder, less a threat. It actually sort of touched on it in the article, China’s relationship to Putin vs the West.

It’s sort of going "we see you eyeing off Taiwan, and chumming up to Russia… Please remember that there IS in fact a red line. We’ve told you where it is and if you cross it, you’ll likely destroy us both. Please don’t go thinking that you’ll be fine, because your economy relies heavily on ours, the same as ours does yours. "