Build only if new commits were pushed to Merge Request seem to be not working

### Jenkins and plugins versions report

Jenkins 2.452.3
Gitlab plugin 1.8.1

Environment

```text
Paste the output here
```

### What Operating System are you using (both controller, and any agents involved in the problem)?

Jenkins installed on Mac OS X Ventura 13.5.2

### Reproduction steps

Create a Webhook on Gitlab with the following config:
Push events: All branches
Comments
Merge request events

Create a Jenkins **Freestyle job** which is linked to this web hook and config it the following way:
Build when a change is pushed to GitLab. GitLab webhook URL: http://****
and the config
Push events
Opened Merge requests
Merge request events
Build only if new commits were pushed to Merge Request
Approved merge requests

### Expected Results

The job is triggered only if
MR is created
The push is made to the MR branch

### Actual Results

The job is triggered whenever any push to any branch is done

### Anything else?

There is a suspicion that the issue could be in the following topic, where the ref spec value cannot be set with the recommended value by documentation
https://issues.jenkins.io/browse/JENKINS-73527

### Are you interested in contributing a fix?

_No response_