This isn't why, although I can see why you might think that. The reason is that for me, based on my ear canal, Harman IE2019 just doesn't work. It's also less about preference here and more about variation in anatomy and HRTF. So for example, most 'good' IEMs as far as target compliance goes sound shouty and unnatural to me. Also, it's worth checking out the paper on segmentation from Olive, Welti and Khonsaripour: https://www.aes.org/e-lib/browse.cfm?elib=20289 , as well as Design Criteria for Headphones: https://vbn.aau.dk/ws/portalfiles/portal/227875122/1995_M_ller_et_al_AES_Journal_a.pdfFor example, the Truthear is a bit over target bettween 1 and ~3 kHz, which can make for a somewhat 'shouty' sound, and can be particularly bothersome compared to inaccuracies in other parts of the frequency response
This is extremely important, and often gets missed in these discussions because we just look at deviations from the target and think "that's why you hear it this way". In reality, we shouldn't care as much about strict target compliance, or overly rely on that to explain reports.