I agree, using the exFAT is also possible, but it does not store the file permissions and ownership. A copy of the same ‘backups’ directory on the exFAT-formatted USB flash drive looks like this:
# ls -lhR /media/usb0
/media/usb0:
total 64K
drwxrwxrwx 1 root root 32K Jan 23 15:20 backups
-rwxrwxrwx 1 root root 334 Jan 29 03:30 exfat_usb_key.txt
/media/usb0/backups:
total 128K
-rwxrwxrwx 1 root root 130 Jul 10 2019 40-backup.rules
-rwxrwxrwx 1 root root 74 Jul 25 2019 backup.disks
-rwxrwxrwx 1 root root 58 Jul 21 2019 backup.sources
-rwxrwxrwx 1 root root 12K Jan 23 15:20 borg_autobkp_all_repos.sh
The original file ‘exfat_usb_key.txt’ was owned by a non-root user. This is a clear difference between UDF and exFAT file systems. How important it is to the user is another matter.