That mystery board that we spotted in the X-ray below the battery serves (in part anyway) as an interconnect for the battery, wireless charging coil, and Taptic Engine.

So we have a secondary battery connector for the first time ever in an iPhone, plugging in directly adjacent to the wireless charging coil. We're not sure what Apple was up to here.

We pop out what appears to be a new barometric sensor design complete with ingress proofing o-ring.

All the components at this end of the phone are stuck to the frame with what seems to be a slightly goopier, stickier adhesive than the foamy stuff we remember from last year. Best guess, it's more waterproof that way.