Here are the steps I followed:
* Start with a fresh install of WordPress 6.0.2
* Upload a cover image background
* Upload an image to overlay the cover block.
* Create a new page, add a Cover block, and choose the background image that was previously uploaded.
* On the Cover Block, change the width to full width.
* Add an image overlaying the Cover Block using the second image that was previously uploaded.
* On the Image in the Cover Block, align center.
* Publish page.
The image is aligned left within the cover block.
I tried using the cover block’s change content position option. The option Top Center correctly causes the image to be centered. You can review that version of the page here:
https://dev-rcm-wp-20221006.pantheonsite.io/cover-test-top-center/
Another interesting observation: I can set the image to align right successfully.
I cannot reproduce this on the Twenty Twenty-one theme.
]]>In the meantime you can center your image by placing a Group block within the Cover block and then place the image inside the Group block, and set the image alignment to center.
This should center the image as the Group block has no such issue.