> electrical/thermal/support power ~= compute power.
Yes, and using larger fans decreases the proportional there. Centralized rectifiers reduces the proportional. Google can make it all the way down to 10% overhead power. That's the point they are making.
On many platforms, such as FreeBSD and macOS, the application-exposed ABI for tasks such as "open a file" or "validate this x.509 TLS certificate" mandates that you link to a shared library and call into it using the C calling convention. (libc and Security.framework, respectively.)
Linux is unique in that you can hand-write assembly to perform a system call and have it work across OS upgrades. FreeBSD does not have stable syscall numbers: open() must be a libc call.