Earlier quoted context omitted.
Importantly not just counterfeit chips but also completely legal clone chips. For context, for a long time Windows did not have a driver for the CDC serial communication class out of the box. But FTDI had made good Windows drivers, and their interface was easy to clone. So for a time there was a market for making 3rd-party chips implementing FTDI's interface and copying their USB id to be recognized by their driver[0…
The issue was, if I recall correctly, that the Microsoft CDC driver was quite buggy. This led to the situation where CDC device vendors were unwilling to produce CDC compatible devices, because the default Microsoft driver would be used and, of course, the blame for any bugginess gets pinned on the hardware vendor. Hence the current situation of many CDC-type devices that are intentionally incompatible enough with th…
"The CDC class has been implemented in Windows (since Windows 98), macOS and most Linux distributions. Since Windows 10, no extra information has to be given in the start-up sequence as the operating system now has a generic driver that will be used for CDC. To support older versions of Windows (Windows 7 and earlier), provide an .inf file that associates with the correct driver."
However, these will not support the high-speed bit-banged JTAG mode FTDI chips can perform with the right driver. =3