I think we must accepting that v-shape signature is very appealing for many people, and if the v-shape isn't exaggerating like in APM, this sound is easily liking and maybe wowing too. Many people listening very loud too and a more neutral/reference mids and treble reproduction can be fatiguing. This is, in big part, I think the success of xm3 and xm4. You noticing now that some people, like me, preferring the Accessibility settings of Balance +slight or Vocal + slight (my case), and this two settings are so different than the APM factory sound, but maybe someone listening at high volumes for more time thinking 'this 2 options are fatiguing'.
This is similar with b&w p7 wireless (and momentum 3) but p7w having more mid-bass (more slam and moire thick mids) than sub- bass but having better reproduction of mid-mids up until treble. The tuning of the APM, like the p7w and momentum 3 and momentum true wireless v1 & 2 is very intelligent for a headphone that's main intention is for consumers wanting better sound than xm3, xm4, qc35 and nc700. If you adding in the APM the best anc in the market today and other features, the success of the APM isn't a surprise at all. For factory sound I preferring shure aonic 50, h9, p7w (only a little) and specially h95 but I can understanding people (average consumers) preferring the sound of the APM than the 4 others.