Block editor: Text goes edge-to-edge with Gutenberg 14.0.0 on some themes

[aisajib]

Description

With Gutenberg 14.0.0 installed, there's an issue that's causing text in the block editor to go edge-to-edge. The frontend remains unaffected (when you preview or publish the post).

Additionally, the issue is only present on classic (non-FSE) themes.

Step-by-step reproduction instructions

1. Install the latest version of Gutenberg (v14.0.0).
2. Install and activate a classic theme (Twenty Twenty, for example)
3. Go to Posts → Add New.
4. Type some text and notice that the text is edge-to-edge.

Screenshots, screen recording, code snippet

Here's a screenshot with Twenty Twenty active but Gutenberg v14.0.0 deactivated. (The expected result)

Here's with Twenty Twenty and Gutenberg v14.0.0 both active.

Environment info

Tested this on:

• WordPress 6.0.2
• Gutenberg v14.0.0
• macOS 12.5.1
• Google Chrome 104.0.5112.101 (Official Build) (arm64)

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

No

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

Yes

[priethor]

I can reproduce the issue as well. It's also affecting make.wordpress.org blogs.