In this scenario traffic needs to go through server A (apache reverse proxy) and then through server B (the SAP WebDispatcher).
Server A = sap.company.com
Server B = webdisphostname.internal.systems.com
The problem is that https://sap.company.com/sap/bc/ui5_ui5/ui2/ushell/shells/abap/FioriLaunchpad.html is being redirected to http://webdisphostname.internal.systems.com:8020/sap/bc/ui5_ui5/ui2/ushell/shells/abap/FioriLaunchpad.html (AS ABAP and WDP running on same host).
Server A has no knowledge about the hostname of the application and the port (8020), so I think it must be a misconfig in the WDP.
Note that we want the end user only to see sap.company.com.
PS. There is no primary tag for SAP WebDispatcher?