Dumont (and all early flyers) used headwinds to increase effective airspeed at takeoff. Does that disqualify him? The Wrights also of course used headwinds and then added catapults to reduce their dependence on ideal headwinds to enable faster progress in a wider range of conditions.

For decades most orbital rockets took off in an easterly direction, effectively using the earth's rotation as a catapult. Does that disqualify them as successful orbital flights?