Jensen named the parts of the Zobel Rdamp and Cdamp which clearly tells its purpose. I do not know of any phono stage inputs with those parts intentionally in placeI do, it retails for $3500 and has had stellar reviews.
It would be interesting to see the response without the Zobel in place to see what it is hiding.It supposedly minimises internal ringing in the transformer.
If you simulate the load of the cartridge and run a square wave through the scope you can adjust the zobel to suit. In the afroementioned phono stage I have personally exerimented with altering the zobel to match the internal imedance of the cartridge, it is clearly audible.
The reality is that transformers are non linear in both amplitude and more importantly phase. It is the phase anomalies that kill the music - musical timing and natural harmonics are destroyed by phase anomalies.
In my experience, with an array of moving coil stepup devices to hand including both tube and solid state active, and many much vaunted transformers, is that active devices, for all their faults are more musically compelling.
Play any jazz record where there are changes in tempo within the track and a comparison between a competent active stage and a competent transformer will highlight the transformers destruction of phase and timing. Look at the bottom end in your graphs - its there for all to see.