Elsewhere Hackaday links to a Russian microelectronics company's blog[1], where they decapped real and fake FTDI chips and found that:
"It seems that in this case Chinese designers implemented protocol-compatible "fake" chip, using mask-programmable microcontroller. This way they only needed to redo 1 mask - this is much cheaper than full mask set, and explains a lot of redundant pads on the die. Fake chip was working kinda fine until FTDI released drivers update, which were able to detect fake chips via USB and send only 0's in this case. It was impossible to foresee any possible further driver checks without full schematic recovery and these hidden tricks saved FTDI profits."
