Thank you for your observations.
The end result is not just a function of the pads, but also the open (Elear, Clear, Utopia) vs closed (Elegia) design of the headphones.
With an open headphone, you cannot just seal the headphones more tightly with pads, because the sound will leak from the open back.
With closed headphones the pads have much higher impact on the headphones acoustic resistance (of the leak). Thus the overall impedance also changes, just by changing the pads [Physical characteristics of headphones used in psychophysical experiments, Tatsuya Hirahara, Acoust. Sci. & Tech. 25, 4 (2004)].