I was referring to the Chinese copying old US stamps, like they do the coins.
Haven't heard any rumors yet. Printing truly engraved designs from scratch is possible but not likely. Correct ink and paper would still be major problems. Collector-experts, dealer-experts and expert groups would detect fakes rather quickly. Plus fakes of valuable modern lithographed stamps are easier to do.
I would be more wary about repairs, adding margins or piecing together a stamp from two or more faulty ones. I've examined covers in the past that were extensively repaired, with or without a "before" photo on hand. Some were really amazing works, even under magnification, blacklight, fluid, though there was typically something "off" enough that the item became suspicious. That something could be just looking too good to be true for a 100 to 150-year-old cover.