I find this hard to believe.

For one thing, there are very many printers out there that only print black-and-white. I happen to own one of the most popular models, which (when I bought it) was the most popular printer being bought on Amazon. It takes black toner only.

There are also many printers out there whose IP addresses are meaningless, because they're on a private network. My home printer has an IP of something like 192.168.1.4, which is what my common-as-dirt home wifi router gave it. So, it's not going to be very helpful to know the IP of the printer or even the computer that sent the print job.

Yes, there are many circumstances where these problems don't apply, and yes, there are undoubtedly people out there trying to falsify evidence who wouldn't know to take any of the simple steps necessary to defeat "hidden fingerprinting" like this. But it seems so unreliable that I would be surprised if vendors even tried.