It seems to me that the issue here is answering the question, "How much risk are you willing to accept?" For me, flameware is on the pernament "no-no" list. Oil lamps are also on the "no-no" list and always have been. (Could have made a FORTUNE back in the day!)
For me personally there are two categories of "risks" involved: 1.) Ethical standards risks. 2.) Legal liability risks. Unfortunately, niether has easy answers.
I'll deal only with #2 here.
The problem with the "do not put in preheated oven, allow to cool naturally" approach is that the description needs to stay with the piece for the useful life of the piece to help protect both you and the user. Paper additions get lost. Legally... I'm guessing that a sharp lawyer would contend that you should have expected that would happen to the paperwork and if the admonition was truly necessary, made provisions to warn all the users of your product not just the original sale owner. Hang tags and product inserts DO get lost.
My own personal attempt at a type of solution to this liability issue a while back was to have a stamp made that said "Do not burn unattended." for some incence burners I was making. Unfortunately that stamp on the bottom looked like crap, and tended to move the feel of the work from that of "fine craft" toward that of "commodity". Not the idea I want with my work. Difficult. Fix one issue... create another.
Another factor in the "legal liability" side of things is how much you actually have to lose. If you are literally a "dirt poor" (pun intended) potter......... even if someone is harmed by your product..... the liklihood of getting sued for damages is kinda' small. To quote Janis, "Nothin' from nothin' leaves nothin'." Such liability suits are usually "contingency fee" based, and a lawyer will usually only take one on if they see a reasonable paycheck possibility.
But if you are a bit more affluent, maybe because pottery is a second job to the 'big money' job, you are retired from a previous well paying career and are now doing pottery, your spouse has a high paying job, and so on... that is potentially a very different story. Unless you are a corporation, (like a LLC) then the assets that you (and your spouse) have (homes, stocks, all studio equipment, etc.) are at risk in any potential liability situation. Even if you "have a business" and file a Schedule C. A sole propietorship does not protect personal assets.
Some would argue that having liability insurance will attract the contingency lawsuit. A valid thought. Again.... no easy answers.
If you are concerned, at the minimum get yourself product liability insurance. The Potters Council has it for members (plug, plug, plug ). ACC has it for members. CERF has it for members. Any insurance agent can get it for your business. If you are typical, it'll cost you less that $1000 a year. Cheap really for the protection and peace of mind. And maybe look into setting up a LLC for your pottery business; it is not hard and not expensive.
As to the technical side of the bakers......... you have to test them .......a lot. Don't assume. Do the "stupid stuff" that a consumer likely will do with it and see what happens. They will. Take it out of the dfreezer and put it in a pre heated oven. Someone will. It is for THOSE people that you have the liability insurance