This is true. USB parallel ports are only implemented far enough to get printers working. Pretty much nothing else from the dark ages will work.
Serial ports are a bit better, but still have compatibility issues because most of them just use TTL level (5 volt) signaling, whereas RS232 specified 12 volts. The better ones have voltage multipliers onboard that will provide the necessary higher voltages; if you want to hook up vintage terminals to your computer using a USB serial port, these are often required.