Given that the effect of using a clone is that the device name is replaced with the message "THIS IS NOT PROLIFIC PL2303. PLEASE CONTACT YOUR SUPPLIER.", it seems pretty clear that this is intentional sabotage.
Your definition of sabotage is quite broad and creative. There is no damage to the hardware. The driver is simply not operating with hardware that Prolific didn’t get paid to support.
If a disgruntled employee went into the office one night and changed all of the computers to not try to boot from the hard drive anymore, would that not be sabotage, just because it's possible to undo?