C Is Not a Low-level Language: Your computer is not a fast PDP-11.

https://spawn-queue.acm.org/doi/10.1145/3212477.3212479

As a corollary, all processors are C VMs, anyway.

It may not be an abstraction of a real machine. But the C abstract machine is very close to the foundational idea of how a computer work. And it’s quite easy to bootstrap.

Importantly my work involves me often being able to look at C and think about the assembly and back and I regularly work on ESP32, ch42(riscv) and atmega avr8.

I couldn't do that with mciropython on any platform.

C is a thin abstraction, python isn't.

How much of it are C extensions not covered by the language standard?

they're technically not wrong. C is literally an "abstraction" of the machine. As we know, the whole point of an abstraction is to ignore the multitude of details :-)