The commit-msg hook is not invoked by git-merge as specified in documentation

Hello,

At least two places in the git docs it is specified that the hook "commit-msg" is invoked by both git-commit and git-merge.

https://git-scm.com/docs/githooks#_commit_msg
https://git-scm.com/docs/git-merge#Documentation/git-merge.txt---no-verify

I'm experiencing a different behavior however. The hook seems to work fine on git-commit, but is not invoked by git-merge.
When I use git-merge my text editor opens with the default message, but when I close the editor the hook is not invoked as I would expect.

For reference, the prepare-commit-msg hook works with both commands as expected.

Is there something subtle I'm overlooking?
Of course a fast forward merge should not invoke the commit-msg hook, because no commit is made.
But in my tests with non FF-merges the hook is still not invoked.

Kind regards,
Kalle Kromann
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