But honestly... does it really matter how small your executable is? I'd care a lot more about performance characteristics than binary size.
[1] http://www.muppetlabs.com/~breadbox/software/tiny/teensy.htm...
Of course, this is just an approximate general rule, and extremely small binaries (and generally any "pointless" experimentation) like this are mainly interesting from a learning point of view (or for small embedded microcontrollers), e.g. understanding syscalls and program start-up, and, for the write-up you link, the ELF format. (Not everything has to be inherently useful for an actual task.)
The key word here is I'd. The programming world is vast, and the range of hardware is likewise vast. So, so vast. Really huge. Pick a restriction you don't have to worry about; someone else out there does.
It demonstrates how much control you can choose to exert over your compiled program.
So we already knew that about assembler, now we also know Rust can be twisted quite close to that too.