Hey
@perspectionist -- any word from S & B?
Take everything I am about to say with a grain of salt because I am not a lawyer, and this is not legal advice. But, as a legal "hobbyist," your question intrigued me a bit.
I think S & B would have to argue you used some sort of non-approved herb in the device and connect that to the reason for warranty rejection for it to have any bearing in court. The device vaporizes lots of things at 190 degrees C - including three things with medicinal application in the manual: Sage, Thyme, & Chamomile. There isn't any reason for you to disclose what you put in the device and your use is consistent with vaporizing those three herbs.
S & B is probably not wanting to wade into that legal water either. At that point, it raises questions about what they are doing shipping a device they know to have cannabis residue across state lines. (Hint: This is probably why S & B says "Ship us only your Crafty base, and not your cooling unit" on a warranty swap -- because they don't want the liability of being on the receiving end of dirty cooling units full of thc buildup and getting pwned by the US Federal Government for participating in interstate drug trafficking).
Now that I am thinking about it more, though, you might have to appear in court in CA to sue S & B in small claims court -- but you might have some recourse with the California Attorney General's office...