Yes, the 4.A has gotten good reviews on HF, but shouldn't the detail be very similar for earphones that have the same basic armatures? I'm thinking choice of acoustic filters plays a role as well.

I can confirm from the pictures that the damper filtering the DTEC is the same red 2200 ohm damper as the one used in the 4.A. I can't be sure as to the damper choice in front of the TWFK, because it's possible that it's grey (330 ohm), white (680 ohm), or even green (1680 ohm) as the shell is green so I can't tell. I'm willing to make an educated guess that it's white, though.

Regarding detail, I think it's less about the articulation of the drivers themselves and more about the crossover enabling linear phase response and a frequency response that enables transparent sound. A more advanced driver would definitely change the sound, but judging from the notch recorded and the relative levels of the peak amplitudes, I still say they look similar.

It'd be nice to see a CSD plot of the C4, and hopefully the 4.Ai as well. That'd give us a good idea of how close together the two are, though variances will happen because of the universal tip vs. custom sound bore, etc.