Multi-project pipeline trigger does not appear to trigger pipeline with a trigger like you would expect

Using a multi-project pipelines I am expecting to trigger a pipeline the same way I would with a trigger token, for example:

gstg-qa:
  stage: gstg-qa
  trigger:
    project: gitlab-org/quality/staging
    strategy: depend

Would trigger the this project the same way as :

curl --request POST --form "token=$CI_JOB_TOKEN" --form ref=master https://ops.gitlab.net/api/v4/projects/263/trigger/pipeline

What I see instead, is that the downstream jobs are not triggered jobs, but the jobs we have defined for initiating a pipeline normally:

The problem is that the documentation is unclear:

Interesting, it seem to react to only: [:pipeline] which corresponds to dependent pipeline, instead of trigger.

This to some extent does make sense (the :pipeline) as this is external pipeline.

This works for https://docs.gitlab.com/ee/ci/multi_project_pipelines.html#triggering-multi-project-pipelines-through-api.

It behaves exactly the same as:

curl --request POST --form "token=$CI_JOB_TOKEN" --form ref=master https://ops.gitlab.net/api/v4/projects/263/trigger/pipeline # it will have source :pipeline

This is also considered to be of source :pipeline. :trigger is used by Settings > CI/CD > Pipeline Triggers.

So, the problem is that our documentation is not very good on these regards, as it should clearly mention that you can filter by CI_PIPELINE_SOURCE == :pipeline it means, that this pipeline is triggered by another pipeline (we know exactly the job that is triggering this pipeline).

Consider, that this is different to:

curl --request POST --form "token=$PIPELINE_TRIGGERS_API_TOKEN" --form ref=master https://ops.gitlab.net/api/v4/projects/263/trigger/pipeline # it will have source :trigger