It's not the EQ that causes the distortion when you try to boost frequencies it's a shortfall of the entire system to produce the boost you are requesting with the EQ settings. To make a blanket statement that boosting causes distortion is not true.
I never believed in the one curve fits all theory anyway and I thought this whole post never made a lot of sense to begin with. There is no absolute right or wrong when it comes to sound. All that matters is that you like what you hear.
09 E90 M3 - Interlagos Blue / Black Novillo / Sycamore Anthracite / Eibach / HRE