Those china dishes with an unglazed bottom are the ones with a thin unglazed ring on the underside. China dishes with a glazed bottom actually exist. There are even china dishes with a glazed bottom that are the exact same type of dish as an already existing one with an unglazed bottom. China dishes with an unglazed bottom repeatedly laid on top of other china dishes can eventually scratch a hole through the glaze layer which might be as bad as having a chip for introducing bacteria. Some restaurants even have a policy to throw out all dishes with a chip or a crack. Please find a way to train people on where to buy a china dish with a glazed bottom of any shape they want that exists and then companies that produce dishes with an unglazed bottom will start losing money and then feel the pressure to make the effort to learn how to produce ones with a glazed bottom.