My takeaway was that you're always writing against a machine. The difference is whether you're writing against a physical hardware machine or an abstract virtual machine. OSes and VMs abstract over existing machines and present a virtual interface for the sake of portability, but they're still themselves machines.

You're still coding against a machine, and you still have to spend time learning the vicissitudes of that machine. But you also have the impedance mismatch between the virtual machine you're developing against and the physical machines you intend the software to run on. All software abstractions are, to some extent, leaky.