> No. There is nothing reasonable about this. This is programming. When you're programming against a spec (POSIX), you don't "make assumptions". You rely only on what it says in the spec.

Are you sure 100% of Linux application developers first and foremost think about POSIX, and never rely on an implementation-defined oddity to get the behavior they need?

Hyrum's Law is powerful: "With a sufficient number of users of an API, it does not matter what you promise in the contract: all observable behaviors of your system will be depended on by somebody."

> People are quick to lazy it out, assume, copy-paste, etc, instead of critically thinking "wait, does the code I write here really guarantee the desired effect, e.g. to write my file to disk".

Exactly. That is a fact of life that Linux kernel developers have to balance with POSIX.