Merge Request pipelines ignores only `changes`

Summary

With only and except (complex) the docs say that the keys are put together with an AND. On merge_requests pipelines all jobs are always run even though they don't contain changes in the specified folder.

Steps to reproduce

Create a .gitlab-ci.yml and a job with the following only setting, open an MR for it and push a second commit with changes outside of the api folder:

only:
  refs:
    - branches
    - merge_requests
  changes:
    - api/**/*

Example Project

https://gitlab.com/cmd_h/example-only-changes-mrs cmd_h/example-only-changes-mrs!1

What is the current bug behavior?

All jobs on the MR are always run even though changes have been to a folder not matched in only.

What is the expected correct behavior?

For the latest commit on the open MR, no job should have been run as it contained only changes to the frontend folder.