The Heading IDs returned via REST API are different than the ones rendered in the UI

Issue Summary

The heading IDs returned by the Get content REST API endpoint are different than the ones rendered in Confluence UI.

This is not an issue on pages using the legacy editor (it only seems to happen in the new editor).

Steps to Reproduce

1. Create a page with a heading (e.g. page title "new page", with a heading 2 text saying "Heading Two")
2. Click on the icon to copy the link to heading and paste it somewhere
3. Open the developer console and find the Heading ID
   
4. Call the Get content REST API endpoint and find the Heading ID in there too:

   https://<instancename>.atlassian.net/wiki/rest/api/content/<page-id>?expand=body.view

5. Compare the Heading IDs collected in steps 2, 3 and 4

Expected Results

The IDs are the same

Actual Results

The IDs are different ("Heading-Two" in UI and link copied, "HeadingTwo" in the REST API response body):

Heading link copied:

https://NAME.atlassian.net/wiki/spaces/{KEY}/pages/{ID}/New+Page#Heading-Two 

UI (Dev Console):

<h2 id="Heading-Two" ... >

Rest API:

<h2 id=\"NewPage-HeadingTwo\">

Workaround

No workaround available at the moment.