As far as I know, it's impossible to merge a GitHub pull request without one of squashing, generating a merge commit, or rewriting the commits. It is not possible to simply copy pre-existing commit IDs.
You can test this yourself. Simply checkout the main branch, add two new commits, push those commits to a dev branch, and try to merge them in a PR to main in a Rebase: you will observe that github has rewritten the commit IDs vs. the ones you generated locally on commit.
