Right now I have to lean my phone on my purse to get a nice reading angle, because the lens block is lopsided and my phone wobbles around otherwise. The Air bump is still a better angle than flat, and I bet the lens doesn’t keep it from resting stably on the lower edge of the chin (?) rather than the lens edge.

No, it wobbles and doesn’t rest on the lower chin. Look at the Verge hands-on video on YouTube.