There is no need or indeed possibility of formatting a partition of the internal disk.. It is now and forevermore HFS+ format.. but that makes no difference to windows which is connecting by network.. to SMB resource..
The main issue is that TC will be treated as FAT32 with all the problems of file sizes greater than 4GB.
Let me say it is possible to create a virtual disk on the TC.. in much the same way Time Machine does for the Mac.
See
Possible to create a windows VHD file on the TC.. format it GUID/NTFS and mount it to the windows computer.. Windows believes it is NTFS formatted.
From Finder it looks like a single large file just like sparsebundle.
https://discussions.apple.com/thread/7634417?answerId=30518554022#30518554022
https://discussions.apple.com/thread/7634997?start=0&tstart=0
The big downside here is storing files on a disk in non-native format.. and if you ever need to restore it on a non-working computer.. you are in for a hard time.
Really a USB NTFS formatted drive plugged straight into the windows computer is a lot better backup target than a network disk that is Mac formatted.