core.worktree misinterpreted by Git GUI

I have a "super-repository" tradr-simulation which contains several subfolders. I wanted to share some of the subfolders through another Git repository, so I created an "external subrepository" - the .git resides above tradr-simulation in the filesystem, and in its config I've set core.worktree to point to tradr-simulation (particularly worktree = ../../../tradr-ws/src/tradr-simulation ).

Now here's what's shown in CLI (CWD is the "external subrepo"):

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D:\Programování\tradr-git\non-tradr-share\robot-model>git log
fatal: bad default revision 'HEAD'

D:\Programování\tradr-git\non-tradr-share\robot-model>git status
On branch master

Initial commit

Untracked files:
  (use "git add <file>..." to include in what will be committed)

        .gitignore
        README
        gazebo-test/
        nifti_robot_description/
        nifti_robot_gazebo/
        vrep_ugv_simulation/

nothing added to commit but untracked files present (use "git add" to track)

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However, if I start Git GUI from the "external subrepo", it is somehow misled to think I wanted it to show the "super-repository". In the screenshot attached, you can see how Git GUI looks when called as:

D:\Programování\tradr-git\non-tradr-share\robot-model>git gui

The window title as well as the Unstaged changes correspond to those of the "super-repo", even though I started Git GUI from the "external subrepo" directory.