As stated, in any Professional discussion of helo rotor aerodynamics the effects we are discussing occur on and around on the disc alone. What the fuselage does is entirely a secondary matter of mechanics, not aerodynamics.
The only use of the expression of 'blowback' that I know is always accompanied by a number up to five and ideally followed by a cry of 'Syph on your donk' or some such ribald dimissive.