Registering a lot of meta boxes results in a small editor screen

[websupporter]

Describe the bug
I registered a lot of meta boxes to see what would happen. I was suprised to see a very small editor window and a very huge metabox section, basically disabling me to edit text in a good way.

To Reproduce
Steps to reproduce the behavior:

1. Add a plugin with the following code and activate it

add_action(
	'add_meta_boxes',
	function() {

$i = 0;
		while ( $i < 20 ) {
			add_meta_box(
				'test-'.$i,
				'TEST-'.$i,function () {
	echo '<h1>TEEEEEST</h1>';
},
				['post']
			);
			$i++;
		}
	}
);

2. Go the the editor

Expected behavior
I would expect to have the vertical scrollbar with the metaboxes, not with the editor, so I could have more space with the editor.

Screenshots

Desktop (please complete the following information):

• OS: ubuntu 14.04
• Browser firefox

Additional context

• WordPress 5.0 beta 3

[La-Geek]

I assume, this is the same issue, (meta boxes overlap the gutenberg blocks)
as described there #11378

[designsimply]

Thank you for testing! Closing as a duplicate of #11378.