Have a look here:
It’s not exactly a ban because (I’m pretty sure) it’s not lawful to ban people from taking medical tests. But the government puts strict controls on the importation of certain test kits and (it seems) the way tests are administered by medical professionals, which amount to a ban. Most COVID “rules” around the world are implemented in this way the skirt the letter of the law.
I suspect the people you’re talking to are getting confused between antigen tests and antibody tests, unless their English (or your Chinese) is extremely good.