We finally stumble across some subtle differences in the chipset:

Intel SR346 Intel Core m3-7Y32 Processor (4M Cache, up to 3.00 GHz)

Toshiba TH58XGT0JFLLDVK 128 GB NAND Flash (+ 128 GB on the reverse side for a total of 256 GB)

SK Hynix H5TC4G63CFR 4GB DDR3 SDRAM

Universal Scientific Industrial 339S0251 Wi-Fi module

Broadcom BCM15700A2 (as seen in several other MacBook models, but this version has a notably different form factor)

National Semiconductor 48B1-11 (LP8548B1) display backlight driver

SK Hynix H9CKNNN4GTATMR-NTH (with SSD controller presumably layered underneath)