They've also been tested and licensed to do that. If GE, LG, et al. decide to come out with a new Microwave oven that leaks so badly it effectively is a jamming

They've also been tested and licensed to do that. If GE, LG, et al. decide to come out with a new Microwave oven that leaks so badly it effectively is a jamming device then it won't be licensed and it can't be legally sold.