Why can't I set "merged" Pull Request trigger on GitHub Actions?

I recently used GitHub Actions the first time, then I felt strange.
I often used Bitbucket Pipeline, but I didn't feel strange.

Why?

To feel strange

I used GitHub Actions first time, so I ran it through various settings.

The first, I made .github/workflows directory, then I wrote easy code.

name: example
on:
  push:
    branches:
    - main
    - develop

I push code to main branch or develop branch, Pipeline run.
It's ok, I set push prohibition to main branch or develop branch.

Next, I'd like to pipeline run after pull request is permitted.

name: example
on:
  pull_request:
    types:
      - closed
    branches:
      - main
      - develop

Just a moment, this code is pipeline run by permission or rejection if pull request is closed.

Let's research...but I can't find it.

For example, I'd like to get "merged" value,

name: example
on:
  pull_request:
    types:
      - merged   <＝＝＝ This
    branches:
      - main
      - develop

But this value is nothing.
Oh,,,

Blow link, same question as mine.
https://github.com/orgs/community/discussions/26724

Why feel strange

When I used Bitbucket Pipeline, I don't care about it.
For example Bitbucket Pipeline code.

pipelines:
  branches:
    main:
      - step:
    develop
      - step:

Pipeline run after main branch or develop branch merge.
So pull request is rejected, pipeline don't run.

1. pull request close
2. pipeline don't run

I don't feel strange order of thinking.

but,

1. pull request close
2. pipeline run <=== Why it run?

I have no choice, let's just accept it.

Countermeasure

This code is countermeasure.

if: github.event.pull_request.merged == true

So pipeline run, then pipeline stop.
But history of pipeline remains,,,It's ok.

Finally

I learn behavioral differences at similar services.
I'd like you to teach me same situation, programming language, tech services etc...

Have a good day.