That’s a pretty wild guess given how China keeps doing military drills involving amphibious landings and flying into Taiwanese airspace/going into Taiwanese waters. You wouldn’t practice amphibious landings to prepare a defense against the US, you’d do that to prepare for an invasion. China talks a lot about not using its military outside its borders, which has been mostly true, but they see Taiwan as within their borders so it doesn’t really tell us much.
If China wants to limit imports of goods from Taiwan they absolutely could, and it would be difficult for the US/Japan to respond to, but if by “restricting trade” you mean a blockade then that is an act of war that the US/Japan would respond to much more aggressively. Just like China would respond if we blockaded them.