But the driver doesn't work any differently for their own chips than the old one did. And this change was definitely, unambiguously, breaking clones on purpose.
For all we know, the new driver could have been a rewrite from scratch (say to support new products that run at higher speeds than the older driver could support), and the new driver never worked with this particular clone to begin with.
Keep in mind that the driver developer may not even be in possession of a clone of this type. Clones see new versions over time just like any other product, the only thing is that since they don't advertise their true version, it's impossible to practically support them.
The new driver detects clones, puts "THIS IS NOT PROLIFIC PL2303. PLEASE CONTACT YOUR SUPPLIER." in Device Manager, and refuses to work. What sequence of events do you see that would have led to that string existing, let alone all of that happening, unintentionally?
What I'm saying is that just "don't write code to try to detect clones, and treat every chip the same as you're currently treating official ones" would have been sufficient to make it work, and they intentionally did extra work and wrote extra code to make it not work on clones.
Again, you do not actually know that. If you read what I wrote earlier, then you would understand that there are plausible scenarios where no intentional breakage occurred.
I don't know for sure that it was intentional, but you also don't know for sure that it wasn't. And the existence of the string is quite strong evidence in favor of it being intentional.
For all we know, the new driver could have been a rewrite from scratch (say to support new products that run at higher speeds than the older driver could support), and the new driver never worked with this particular clone to begin with.
Keep in mind that the driver developer may not even be in possession of a clone of this type. Clones see new versions over time just like any other product, the only thing is that since they don't advertise their true version, it's impossible to practically support them.