It does make sense, but then don't we have the same issue with zlib.scm:

--8<---------------cut here---------------start------------->8---
(define gzread!
  (let ((proc (zlib-procedure int "gzread" (list '* '* unsigned-int))))
    (lambda* (gzfile bv #:optional (start 0) (count (bytevector-length bv)))
      "Read up to COUNT bytes from GZFILE into BV at offset START.  Return the
number of uncompressed bytes actually read; it is zero if COUNT is zero or if
the end-of-stream has been reached."
 ...
--8<---------------cut here---------------end--------------->8---

I initially tried to mimic zlib.scm and this part confused me a lot back then.

-- 
Pierre Neidhardt
https://ambrevar.xyz/