Description

Noticed while working on adding tests for #69190

By default, the Post editor has fullscreenMode enabled since a few years.
The Site editor has always been in full screen mode.

However, most of the e2e tests run with the fullscreenMode preferences set to false. This is relevant only for the Post editor but anyways the tests run with the UI in a state that doesn't faithfully represent the default state of the editor UI.

For context: in #69190 I wanted to test what the first focusable element in the page is after page load. I assumed it was the editor 'View Posts' link. However, since the editor isn't in full screen mode, the first focusable is in the WP admin UI instead.

Besides the test edge case scenario, it seems to me the most important consideration is that the UI state in the e2e tests isn't representative of the default UI state. This may lead to unexpected test results or wrong assumptions.

Step-by-step reproduction instructions

• Run some Post editor tests with the --headed flag so that you can see the browser instance.
• Observe the editor is not in full screen mode.

Screenshots, screen recording, code snippet

No response

Environment info

No response

Please confirm that you have searched existing issues in the repo.

• Yes

Please confirm that you have tested with all plugins deactivated except Gutenberg.

• Yes

Please confirm which theme type you used for testing.

• Block
• Classic
• Hybrid (e.g. classic with theme.json)
• Not sure