Main pipeline stuck in pending status if it triggers a child pipeline without strategy depends

Summary

Linking pipelines with trigger:strategy mentioned that

By default, the trigger job completes with the success status as soon as the downstream pipeline is created.

but

To force the trigger job to wait for the downstream (multi-project or child) pipeline to complete, use strategy: depend

which will force the job to wait for the triggered pipeline to complete. But the current behavior is that the job without strategy:depends will wait forever even though the triggered pipeline is completed cause thing main pipeline to stuck in Pending status.

Steps to reproduce

1. Setup project A and project B where job in project A trigger a pipeline in project B without strategy: depends
2. Start pipeline in project A
3. Observe the job for triggering pipeline stuck in waiting state

.gitlab-ci.yml

stages:
- build
- test
- stage
- verify
- deploy

e2e:check:
  stage: verify
  before_script:
    - echo "e2e check b4 script"
  script:
    - echo "e2e check script"
  allow_failure: true

e2e:cb:
  stage: verify
  allow_failure: true
  trigger:
    project: gitlab-gold/triggered-pipeline

Actual behavior

The main pipeline stuck in pending stage because the job status was not updated.

Expected behavior

After successfully triggering the pipeline, the job status immediately update to success without waiting for the triggered pipeline to complete.

Used GitLab Runner version

Running with gitlab-runner 12.7.1 (003fe500)
   on docker-auto-scale 72989761
Using Docker executor with image ruby:2.5 ...
00:41
 Pulling docker image ruby:2.5 ...

Workaround

Trigger pipeline with API but this workaround doesn't allow the main pipeline to see the child pipeline in the main pipeline page.

Possible fixes