> but no amount of tweaking is going to make a turbofan work at supersonic speeds

Sure they can. It's the inlet's job to slow the flow to subsonic. Turbofans have been used on supersonic military aircraft since the 1960's. Go read about intake ramps. Then learn about diverterless supersonic intakes.

You're yelling scam pretty loud for someone that clearly doesn't know basics of the topic area.

Edit: My guess is the engine they're standing in front of is a JT8 of some flavor, which have been heavily used by both military and commercial aircraft.