Group block: multiple wp-container-* classes and duplicate styles per block

[chthonic-ds]

Description

A wp-container-* class is added to a Group block's parent container, with a <style> element inserted after the block markup to help scope layout settings. I notice a second class is also added for no obvious benefit. This results in two separate but duplicate style elements being inserted per block.

Step-by-step reproduction instructions

1. Add a new Group block.
2. In the Block settings panel set Layout > Inherit default layout.
3. Save and visit the front-end page to inspect the source.
4. Notice two layout-related wp-container-* classes have been added to the parent container. Two corresponding style tags have also been added after the block markup.

Expected behaviour

Presuming this is not intentional, I expect to see a single class added to the block container, along with a single corresponding <style> block.

Actual behaviour

Two different classes are added to the block container along with two duplicate <style> blocks.

Screenshots or screen recording (optional)

WordPress information

• WordPress version: 5.8-beta4 but have observed in earlier versions
• Gutenberg version: 10.9.1
• Are all plugins except Gutenberg deactivated? Yes
• Are you using a default theme (e.g. Twenty Twenty-One)? Tested with TT1 Blocks, screenshot from a different theme

Device information

• Device: Desktop
• Operating system: Windows 10
• Browser: Chrome 91.0.4472.114