WebIDE: Committing with "create new branch" starts two CI pipelines


Sometimes I find myself using the WebIDE, especially if I have to create a simple MR. I find it a great functionality for rapid contributions.
The thing is: my personal fork master branch is at Commit X. I open WebIDE to make simple modifications. I commit the modifications and specify “create new branch” so I can later open a MR. This creates two CI pipelines.

It first creates a new branch, launch CI pipeline, commit on the new branch, and launch a pipeline.
Is there a reason for that or can it be considered a bug?

Using GitLab-CE.

I have opened an issue about that: https://gitlab.com/gitlab-org/gitlab-ce/issues/64526