It isn't necessarily flutter that is bad. It is the associated compressor surge that accompanies it. Without a valve that is actuating correctly, the pressurized air charge downstream of the compressor wheel has nowhere else to go but back upstream through the compressor, once the throttle plate is closed.
This is more of a problem with mechanical valves, which used preset spring tension to actuate. For 13 plus models, with the electronic valves, it is likely less of an issue. I haven't looked closely, but I assume the e-valves are actuated by a solenoid, and have no mechanical spring preset.
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