Given the ridiculous speed of Apple's almost-on-the-SoC flash storage, 8GB is fine for basic development workloads.

That's the tradeoff you get with soldered RAM and storage... you can't expand it, but the lack of sockets and shorter PCB trace paths gives a lot of headroom on what is essentially high-frequency analog signalling. The longer the traces the more latency, and the more sockets and vias, the more potential for interference.