100%. I've tried AutoEQ and also manually dialing in the EQ settings from the PDFs and on all the headphones I've tried (Sony Z5/XBA Z5, Sennheiser IE 800, IE 600, HD 6XX, HD660S, Moondrop KATO) they all lose their charm and end up sounding dead.

My theory is the EQ profile to "flat" doesn't take into consideration the specific driver/housing resonance and therefore can't compare to the stock tuning.

On some cases the difference is minimal (like the KATO) but on other cases you loose a lot of detail, sparkle and layering (HD 660S).

I love a tiny bit of EQ, especially in the treble region but changing the whole sound signature never yields good results for me.