Reverse Proxy (Simple) does not translate the External URL into the Internal URL!

Hello,
Problem description:
Assumptions:
The External URL is: https://externalhost.domain.com
The internal URL is: https://internalhost.domain.com
Selection: Simple Reverse Proxy Action
Web Application Setup URL: https://externalhost.domain.com
Fireware 12.8.2
The internal hostname is populated into the internal DNS server.

Issue:
When checking the Reverse Proxy output, it however sends the external url to the internal host! therefore the connection from the external client to the internal host fails.

Knowing that the same Reverse Proxy when configured using the option: (Predefined Set of Reverse Proxy Actions) translates the external URL into the internal URL correctly with the no problem.

I did not find a similar issue within the community.

Is this a known issue related to the Simple Reverse Proxy action Wizard function? if yes, is there a workaround?

Can any one help?
Thanks