Help! How to configure a ScaleOut for a Data model Refresh

Hi All,

We need to have the following configuration with 2 servers where PBIRS is installed :

1. The first one acts as a Front-End server  (interactive report processing)
2. The second one acts as a back-End server, in particular it accepts all the data model refresh requests (scheduled report processing).
3. On the PBIRS confirmation of each server, the scale out section contains both servers

Question is: How can we force that the first one is used for interactive report processing and the second one will perform the data model refresh?

Microsoft documentation is the following (but not clear to me):
https://docs.microsoft.com/en-us/sql/reporting-services/install-windows/configure-a-native-mode-report-server-scale-out-deployment?view=sql-server-ver15

Thanks for your help!

Karim