decurion:
I don’t think it is a true RTO as the aircraft already left the runway.
Having taken off the same aircraft (probably the same tail number) from that runway many times, my subjective conclusion would be a rejected takeoff. My conclusion is supported by the NTSB investigation into the accident:
The NTSB title of its investigation report is:
Aborted Takeoff Shortly After Liftoff
Finding Number 12 of the report:
12. The captain made a "split second" decision to reject the takeoff by reducing the engine thrust. His decision was very likely based, in part, on the perception of available runway to stop the airplane.