it's not your imagination. My thoughts are that part of the problem is that we would need a few more graphs showing us other aspects of the sound reproduction. Forgive me for referencing speaker drivers as that is what I am more familiar with. It applies here as it is still a driver or drivers with a purpose of accurate sound reproduction. While good tonality is the foundation of good sound, that basic graph won't show us why a Raal ribbon or a Mundorf AMT (or a top Be dome or such) makes you say "wow" when listening to a well recorded cymbal or some other instrument. The added detail that can be heard that is missing or seems blurry and faded on lessor drivers is what high fidelity sound reproduction is all about. Graphs such as the step response, intermodulation distortion and the CSD help us "see" the differences that we can also hear (and things we can't hear as well). The magic is in all of those subtle details. All other design parameters being equal in a headphone or speaker, starting with better drivers should provide a better result.
And add to this the complexities of headphone placement and measurements on different human heads and test rigs etc.
Go take a look at some raw driver reviews and you will see many more measurements taken at many SPLs, each illuminating some aspect of the drivers performance and it's ability to accurately reproduce a source signal. When all these graphs are added together we can understand what that mid, woofer or tweeter driver is capable of. I am constantly in awe of how a great driver can somehow replicate the complex tones of a violin played by a talented musician and bring joy
In summation: superior driver has the potential of superior (accurate) sound reproduction and more data graphs are needed to illuminate us as to why that is
Of course I could be wrong as I am new to headphones