Fritz!box -- trying to block myself from the WAN without blocking the modem itself (whitelist seems broken)

I created a whitelist access profile. That ensures that the whole WAN is blocked except what is exceptionally whitelisted. I started with an empty whitelist. The LAN is rightfully accessible and the WAN is rightfully inaccessible.

The router does not use DSL. Instead, it uses a USB mobile broadband LTE modem. The modem has its own website which gives SMS capability. The modem is technically upstream to the router, so it is blocked when the WAN blocking profile is enabled. I want to whitelist the modem so that when I am blocking WAN access I can still reach the web UI of the modem and monitor SMS msgs.

Fritzbox is designed so that all attempts to directly access an IP is blocked if whitelisting is in play. IP addresses cannot be whitelisted, only URLs using FQDNs. So I did “nslookup 10.10.50.8” to get the hostname of the modem. Then I whitelisted the hostname. That does not work. The modem is still blocked.