editor-expand.js DFW button remnant causes intermittent TinyMCE editor height miscalculation in WordPress 7.0

[MadtownLems]

Disclosure: This is an AI-assisted bug report. I've done my best to investigate its accuracy, but it's a bit out of my area of expertise. I used AI to help debug the problem that I noticed.

In WordPress 7.0, the Distraction Free Writing (DFW) button no longer appears in the TinyMCE toolbar, indicating the feature was removed or disabled. However,wp-admin/js/editor-expand.js still contains code that registers the DFW button with TinyMCE and immediately hides it during the editor init event:

editor.on( 'init', function() {
    if ( button.disabled() ) {
        button.hide();
    }
} );

This button.hide() call triggers a TinyMCE reflow/repaint cycle (via theme.js) at a moment when the new React-based admin UI introduced in 7.0 has not finished laying out. The result is an incorrect height being stamped onto #mceu_31-body, causing the TinyMCE editor area to render with a large empty gray space.
The bug is intermittent because it is a race condition between React finishing its layout and TinyMCE firing init. It reproduces most reliably on a hard refresh (Shift+F5).

Steps to reproduce:

• Install WordPress 7.0
• Use the Classic Editor (either via the Classic Editor plugin or add_filter( 'use_block_editor_for_post', '__return_false' ))
• Open any post for editing
• Hard refresh (Shift+F5) repeatedly until the bug appears

Expected result: TinyMCE editor renders at the correct height.
Actual result: #mceu_31-body receives an inflated inline height (e.g. 459.391px) while the inner #content_ifr iframe is a normal size, leaving a large gray gap.
Root cause: The DFW button registration and hide logic in editor-expand.js was not removed when DFW support was dropped in 7.0. Removing that block should resolve the issue.
Workaround: None confirmed beyond avoiding hard refreshes.

[MadtownLems]

screenshot of overly large gray area in tinymce

[jorbin]

The DFW button wasn't removed in 7.0. While using the classic editor plugin on a stock version of WordPress, it appears as expected. See screenshot

I'm noticing that in your screenshot, you have a number of additional buttons that seem to be from plugins. Are you able to replicate this issue on a stock (no plugins and using a default theme) version of WordPress?

[MadtownLems]

The DFW button wasn't removed in 7.0.

The plot thickens! For me, on a brand new stock (LocalWP) instance of 7.0 with classic editor plugin, i do NOT get the distraction-free-writing icon. 😮

In looking further, I found this ticket https://core.trac.wordpress.org/ticket/62676 which feels incredibly related.

@joedolson - any luck investigating that ticket and seeing if it's related to this issue?