All commits added to changelog after merging a branch containing a release

#### TL;DR

After making a release with release-please on a "hotfix" emergency branch, I rebased on `main` and squash merged the hotfix branch to `main`. After creating a release pr on `main`, all commits since the beginning are added to the changelog.

#### Expected behavior

The changelog contains only the commits since latest ("hotfix") release.

####Observed behavior

The changelog contains all commits since the beginning of the repo.

#### Example repository

https://github.com/loderunner/devexp-flow

* the 1.1.1 release is the hotfix release
* the 1.2.0 release PR is the next trunk release
* the [1.2.0 release PR changelog](https://github.com/loderunner/devexp-flow/pull/15) shows all commits since the beginning
* [comparing 1.1.1 to `main`](https://github.com/loderunner/devexp-flow/compare/1.1.1...main) only yields 3 commits, that are the ones I expect to see in my changelog

#### Environment details

- OS: Ubuntu 20.04.6 LTS
- Node.js version: 20.2.0
- npm version: 9.6.6
- `release-please` version: 15.12.0

#### Steps to reproduce

1. Initialize `release-please` on a node project with `release-please bootstrap --type node`
2. Add a feature commit on `main`, `git commit -m 'feat: initial commit'`
3. Create a GitHub release on `main` with `release-please github-release --target-branch main`
4. Add a feature commit on `main`, `git commit -m 'feat: some feature'`
5. Create a release PR on `main` with `release-please release-pr --target-branch main`
6. Create a `hotfix` branch based on latest release (before "some feature") `git switch -c hotfix 1.0.0`
7. Add a fix commit on the `hotfix` branch, `git commit -m 'fix: some fix'`
8. Create a release PR on the hotfix branch `release-please release-pr --target-branch hotfix`
9. Squash merge the release PR into the `hotfix` branch
10. Create a release from the `hotfix` branch, `release-please github-release --target-branch hotfix`
11. Rebase the `hotfix` branch on `main`, `git rebase main hotfix`
12. Open a PR from `hotfix` to `main` and squash merge it (commit message 'fix: some fix')
13. Update the release PR on `main`, `release-please release-pr --target-branch main`

If I didn't get this wrong, the release PR changelog _should_ include `feat: initial commit`. Feel free to ask me follow-up questions as this scenario is drawn from memory and might not work.