I am sure that you are not starting a fight.
I think though that it should not be "resonance" as we understand the term. Resonance requires that the blades shift so that the rotor becomes unbalanced - like a washing machine trying to spin with an unweighted load. The design of the R44 rotor head precludes that unless it is significantly broken or FOD is picked up in the rotor and then lifting-off would be exactly the wrong reaction.
I can accept that vibration led the pilot to conclude that he had to lift. I can accept that the wooden structure may have played a part in leading him to that decision.