I don't know who this designer it is whom you spoke to, but it seems that the curvature and materials of most phones nowadays are specifically chosen to provide a more slippier and uncomfortable grip, making it all the more likely that it slips out of a users hands especially in tense situations.

The grip of my Samsung without a phone case is anything but secure. And like other commenters already mentioned here, you can't put down your phone on any kind of surface without a case, as it could scratch the camera housing.

You have only a few valid points that actually make sense like 'added bulk' and 'impaired heat dissipation', but still don't take away from the additional safety and grippiness that cases offer. I use a wireless charger and never ever had to once remove my case to charge the phone. Neither has the case ever "partially covered ports or buttons", that made charging or operations difficult.