Machinbird
That may be true, but that central "combustor" with the convergent divergent nozzle is so close to one in geometry that there isn't much difference.
In terms of exhaust velocity, you're right. Regardless, rockets aren't air breathing, and this engine is.
I suppose the real question is whether or not the head end of that combustor is closed and able to develop high chamber pressures or not.
High chamber pressures would be consistent with a rocket right?