As originally discussed in #35400 (comment), it looks like the Heading component may currently not fit the needs of the most recent designs (specifically for the Global Styles sidebar, in this case)

We should assess the situation and, if necessary, decide how to proceed in order to have a component offering the new heading styles needed for the Global Styles sidebar UI.

Examples that came up recently:

• ToolsPanel: Remove hardcoded classnames #35415 (comment)
• Enable always on burger menu for responsive navigation menus. #35568 (comment)
• Fix-up Post Editor’s preferences modal #35369 (comment)

Useful links:

• Component's definition and code: https://github.com/WordPress/gutenberg/tree/trunk/packages/components/src/heading
• Storybook example: https://wordpress.github.io/gutenberg/?path=/story/components-experimental-heading--default