Did they recommend or just say that it could be used in a different way?
There is a whole world of difference between being told to do something and being told it's possible to do something.
It's generally common sense that if you buy something and use it in a manner different to how it was sold you are taking a risk, the only possible comeback (in my non legal background) is if you are told explicitly to do it rather than it's a something that is possible.
I've bought a number of DVD drives over the years knowing it's possible to flash them to get them to work in a manner other than which they were sold, and knowing that by flashing them I'm taking a risk that any warranty might be voided (generally to either make them region free or because the same hardware had different firmware versions by different manufacturers - HP for example I think used to use their own firmware to rebrand Lite-on drives).