Plug in the claimed numbers. At 1kW in, it generates 1.2mN of thrust. At 100km/s that is a power of 1.2kW. Clearly such over-unity numbers are bogus, and the only place for bogosity to enter in is in the 1.2mN/kW. That's why it must be bogus.
I'm not arguing; I'm ignorant and genuinely curious. (My last formal exposure to physics was over 35 years ago.)
Can you explain why this same reasoning wouldn't apply to any constant-thrust drive, such as a laser or microwave drive? Is it a matter of the thrust/power ratio? Is the "no-perpetual-motion" argument not that the EM drive can't produce any thrust, but that it can't produce so much?
You mentioned elsewhere that you support light-sail research. Hypothetical: Shine an ideally-focused laser upon a light sail. Does the light sail maintain a constant acceleration up to relativistic speeds?