df.exe does not report status of network filesystems like SMB, NFSv3, NFSv4.2 (ms-nfs41-client), CephFS, ...

Start at the df.exe entry point and reproduce the issue with the listed SMB, NFS, and CephFS network filesystems. Trace how filesystem status is enumerated on Windows, then verify that network mounts report filesystem, capacity, usage, and mount-point data like the Cygwin and MSYS2 examples; the issue names no test file.

df.exe does not report status of network filesystems like SMB, NFSv3, NFSv4.2 (ms-nfs41-client), CephFS, ...

$ df.exe
Filesystem 1K-blocks Used Available Use% Mounted on
\?\Volume{f6d90251-0739-4aa9-a981-408113eb268c}\ 401980180 270931472 131048708 68% C:
\?\Volume{9f160871-d1b8-11ef-8c9b-806e6w6e6963}\ 6010038 6010038 0 100% D:\

Cygwin and MSYS2 df.exe eport all filesystems:
$ df -k
Filesystem 1K-blocks Used Available Use% Mounted on
C:/cygwin64 401980180 270931584 131048596 68% /
H: 1953514584 1774552848 175195264 92% /cygdrive/h
D: 6010038 6010038 0 100% /cygdrive/d
E: 31997344 2723256 29274088 9% /cygdrive/e
F: 123869696 45786728 78082968 37% /cygdrive/f
I: 1953514584 1774552848 175195264 92% /cygdrive/i
J: 500107608 303016512 182767216 63% /cygdrive/j
L: 500107608 303016512 182767216 63% /cygdrive/l
M: 500107608 303016512 182767216 63% /cygdrive/m
O: 500107608 303016512 182767216 63% /cygdrive/o
P: 500107608 303016512 182767216 63% /cygdrive/p
R: 436336 0 436336 0% /cygdrive/r
T: 436336 0 436336 0% /cygdrive/t