safe.directory and use of %(prefix)/ for UNC paths

[csware]

Setup

• Which version of Git for Windows are you using? Is it 32-bit or 64-bit?

$ git --version --build-options

git version 2.44.0.rc0.windows.1
cpu: x86_64
built from commit: 5cff971ba4c5c91f881d277bfeb6a88fa8c17745
sizeof-long: 4
sizeof-size_t: 8
shell-path: /bin/sh
feature: fsmonitor--daemon

• Which version of Windows are you running? Vista, 7, 8, 10? Is it 32-bit or 64-bit?

$ cmd.exe /c ver

icrosoft Windows [Version 10.0.19045.3996]

• What options did you set as part of the installation? Or did you choose the
  defaults?

Editor Option: Notepad++
Custom Editor Path:
Default Branch Option:
Path Option: Cmd
Plink Path: C:\Program Files\TortoiseGit\bin\TortoiseGitPlink.exe
SSH Option: Plink
Tortoise Option: false
CURL Option: OpenSSL
CRLF Option: CRLFCommitAsIs
Bash Terminal Option: MinTTY
Git Pull Behavior Option: Merge
Use Credential Manager: Enabled
Performance Tweaks FSCache: Enabled
Enable Symlinks: Disabled
Enable Pseudo Console Support: Disabled
Enable FSMonitor: Disabled

Details

Git 2.43.0/2.44rc0 work with safe.directory = %(prefix)///nas/share/repo and also safe.directory = //nas/share/repo. The latter case did not work with older version of Git.

When no safe.directory is set, Git 2.43.0/2.44rc0 say:

fatal: detected dubious ownership in repository at '//nas/share/repo'
'//nas/share/repo' is owned by:
	VORDEFINIERT/Administratoren (S-1-5-32-544)
but the current user is:
	XXX/XXX (S-1-5-21-XXX-XXX-XXX-XXX)
To add an exception for this directory, call:

	git config --global --add safe.directory '%(prefix)///nas/share/repo'

What is the recommended way to set safe.directory? Is the latter one a regression?

It would be great if this case (and related cases such as //wsl.localhost/) would explicitly added to the man page of git-config.