No signed commit for "Sync an out of date branch of a fork from the web"

I used this feature: Sync an out of date branch of a fork from the web | GitHub Changelog

it created a merge commit: Merge branch 'django:main' into always-open-field-file-on-access · graingert/django@50efa6b · GitHub

but it wasn’t signed by 4AEE18F83AFDEB23 and I expected it to be

/cc @canuckjacq

I’m not sure what you mean by “signed” here — but I’m assuming you are referring to the commit hash (unique identifier).

Synching an outdated branch will re-play any commits you have added the upstream branch, hence the commits’ hashes will change. Also, depending on the upstream repository settings and strategy regarding merging pull requests (merge, squash, or rebase), synching an outdate branch might involve rebasing it onto the fetched upstream branch (so, even the upstream commits might have changed their original hashes).

By signed I mean GPG/PGP signed.