> Gambit does what you suggest and also normalizes the path:
>
>> (current-directory "/tmp")
>> (current-directory)
> "/private/tmp/"

Is the normalization done using realpath()? I wonder whether there are
edge cases where that causes problems.

Possibly relevant paper:

Lexical File Names in Plan 9, or Getting Dot-Dot Right (Rob Pike 2000)
<https://9p.io/sys/doc/lexnames.html>
<https://static.usenix.org/event/usenix2000/general/full_papers/pikelex/pikelex.pdf>