IMO the measurement results on his HATS have some issues. It's not the measurements that I'm familiar with. One example is er4's measurements are no where near the one etymotic provides(also what we measure).While I generally agree, even measurements from someone like oratory1990 on Reddit have some extreme features that are not worth correcting to. For example his EQ profile for the DT1990 has a significant correction for a dip around 4 or 5KHz. While I think there's definitely something going on at that frequency, if I apply the full correction for that dip as measured on his industry standard HATS, it sounds just plain wrong.
One also has to keep in mind unit to unit variation. Audeze is notorious for this, but it's generally true that a measurement of the same model headphones as yours doesn't necessarily match a measurement of your exact headphones.
Using the EARS from Minidsp is like much worse than headphones' product variation. The acoustic impedance and the physical dimension is completely fucked up. There's a standard to it, IEC-60318. 60318-4 is for the coupler, 60318-7 is for the head IIRC. ITU p57 and 58 also specify some of the stuff.