Stock EQ's sound different with same Q values. Why is this?

Hi,
I am eq’ing some headphones to optimize them a little better for mixing. I am using the Auto Eq app to eq them to the harman curve. Supposedly this is good for mixing. I type in my headphones name and it gives me eq settings to transfer to a parametric eq plugin. With the same settings on Frequency and Studio EQ, they dont sound exactly the same. Ive tested this by flipping the polarity with the same audio file playing on a separate track and just the plugins engaged with the same settings. Im using 4 bands and they cancel on 2 of them but it seems the higher up the frequencies are the less they cancel. Its only a few DB in the difference and barely audible, but Im just curious why this is. I also noticed other digital eq’s dont completely null either with the same settings. Anybody have any idea why this is?

Thanks

Some digital EQs have different q standards. Q 1 on some EQs is wider than the others and vice versa.