Rewrite Rules not working

Hello,

I have these settings

- WP site: www.dynpage.com
- Static version: www.statpage.com

I have the need to rewrite a specific url in the static version of the wp site.
I added this rewrite Rule to achieve this

https://www.dynpage.com/contact/,https://contact.dynpage.com/
I also tried in case the url rewrite for the static page happends before
https://www.statpage.com/contact/,https://contact.dynpage.com/

Unfortunally the urls are never touched.
How can I achieve this?
There is a hint that "URLs will be first checked to ensure they are part of this site, not an external WordPress site, which would mess up URLs of linked images, etc"
But does that include the new URL too? Is this maybe the reason and I have to postprocess all files with "sed" after the export myself?