Hello @KE1980
You are asking about overriding host header in the request and ability to derive the host name from the IP or FQDN of the back-end pool members.
This is the case for Multitenant backend support.
You can set option Destination host -> Replace in routing rules(Route Type: Redirect)
https://learn.microsoft.com/en-us/azure/frontdoor/front-door-url-redirect#destination-host