The original intend behind the sha1sum.c in gpg4win/src/sha1sum.c was to have a bootstrappable file that you could inspect and compile without dependencies to verify an initial installation of Gpg4win. Because windows had no builtin for this.
Nowadays users can just do:
certutil -hashfile GnuPG-VS-Desktop-3.1.20.7-Standard.msi sha256
So there is no need anymore for a simple tool and we should use libgcrypt.
As it is also used in Kleopatra on Windows for the create checksum command and it is nice to have these unix like tools like "sha1sum.exe" and "sha256sum.exe" etc. maybe with some added GnuPGness like proper estream support for filenames and progress-fd and the usual.
I actually found the create checksums tool useful to scan for changes in a large directory tree. E.g. You create a checksum file at some point over a large tree and then later verify the checksums to see which files have been modified.
While the sha1sum.c from Gpg4win takes the hash algo as a compile flag for me an ideal solution would be if gnupg would create some kind of gpghash.exe that switches between algos either by a command line switch or by its own filename and otherwise behaves from input / output like the standard unix sha1sum sha256sum etc. tools.
So that If I install gpghash.exe as sha1sum.exe it would detect this based on argv[0] and use the corresponding libgcrypt hash algo.