What are your numbers and assessments based on?
I don't recognize any of this in my own listening experience or measurements.
The Audeze "vegan" (micro suede) pads are much softer than any of the HiFiMan pads (though I have no experience with the Focus pads).
In my understanding you will generally maximize sub bass when sealing the pads, while a completely open cup will loose bass and especially sub bass.
Softness does not have a linear relationship to acoustic impedance, which is what matters.
Harder pads can have trouble maintaining seal for obvious reasons and lack of seal means much lower impedance.
That said, generally a harder material is higher density, so if the seal is just as good it will have higher acoustic impedance and will also absorb less vibration (shaking).
Surface area touched is important too for transmission of those vibrations.
The assessment of linearity was based on a free air recording of the HE-6 driver using cheap (but calibrated) Dayton EMM-6 measurement microphone connected into verified linear DC-coupled microphone preamplifier (custom job), later into my Lynx Hilo interface.
When not sealed, reflections from the face were inaudible in my subjective opinion. Tonality was noticeably smoother and slightly lighter, but no rolloff seemed to be present. In fact, if you put them closer than 1 cm from ear or rotated the driver to not be coplanar with the earlobe, you got the usual proximity effect bass boost.
Placing them further away (e.g. 1.5 cm, 2 cm) causes a slight subbass roll with a slight general bass boost, as well as slight high frequency rolloff. My bet would be a planar source converting more and more into a point source, plus additional air absorption.
Placing them yet further cuts bass a lot.