Where can you change the IP pool settings that you mention? I only see the main settings under "network settings" but no other alternates.
For example, my configuration has DHCP turned off, LAN set to 10.10.10.0/24, router IP at 10.10.10.1, and DHCP scope of 10.10.10.50-10.10.10.100 handled through my internal DHCP server.
I note that my Guest Zone is getting a 192.168.7.0/24 configuration and the router is handling all of this.
If this is just an unpublished change from how prior devices (such as my 855) used to work, I am extremely thankful as it does truly separate my networks and protect my data.