I think this whole argument is about the bit of cable (usually flex) from the cooking appliance(s) to the fixed installation. If that has a high enough CSA to be adequately protected by a 32A OPD (which is unlikley), and assuming the fixed cabling of circuit was OK for 32A, then a 32A OPD would be OK in terms of cable protection. Sunray appears to be saying that if that flex/whatever is only adequate for 16A, then a 16A OPD is required because of the (extremely small) probability of the 'partial short'.