>> The low level is: [...]
>>
>> High level: [...]
>>
>> So they sound almost the same.
>
> And if so? This gives freedom to the Scheme world because one does not
> have to stick to POSIX semantics when there are better semantics and
> it allows access to the underlying POSIX features. If one goes through
> the POSIX API, are umasks and pathnames really the only things that
> one would handle differently on the Scheme side?

My point is that if they are so similar, they could be just one API that
is less strictly tied to POSIX. There could perhaps be simple escape
hatches for people who want bare POSIX semantics (such as binding the
current-directory parameter to #f to disable pathname translation).

The current SRFI 170 is already designed with a view to being
implemented on Windows (and not only Cygwin/Msys).

For the people who want strict Unix APIs and nothing else... that's what
FFIs are for :)