Interesting points. Though I have some further thoughts.
An IB cone is not limited to the front surface only. The back of the cone usually "sees" a finite rear enclosure. A pressure wave returning to the front of cone from the listening room is likely to be matched by a pressure wave returning from the rear volume. Only if the IB uses the great outdoors will there be no returning wave to match that arriving at the front. The phase of the returning pressure waves is very unlikely to match cone movement.
How is this "problem" related only to the IB? A reflex system below system resonance suffers driver unloading. Would it too not also suffer from returning pressure waves? Wouldn't the reflex cone drive its own reflex port into an infrasonic rumble?
Wouldn't these returning pressure waves be much reduced in comparison with the originating pulse from the driver cone?
It might be possible to monitor an IB or reflex system driver using the voicecoils as a low impedance microphone. While another IB (or VLF-capable sub) at the other end of the room plays a suitable signal.
Meanwhile: In at least one real-life IB situation: If the driver being monitored was an AE IB15 then I doubt much would be found emanating from the driver terminals with such stiff suspension. My very leaky IB enclosure is subject to the prevailing SW winds but no cone movement has been detected by its formerly worried owner so far.
I don't think we need worry too much about returning pressure pulses from the IB affecting itself. The change in atmospheric pressure from a returning VLF transient is simply too small to have any detrimental effect on sound quality.
I believe The Thigpen Rotary Sub has yet to prove itself as silent as an IB when receiving no signal. Perhaps it needs a folded, tapered and heavily damped labyrinth of sufficient length to avoid unwanted pipe resonances?