Our controller managed DNS feature is not meant to override all DNS on the system. It’s meant to provide an alternate DNS server for a specific search domain for situations like running in a Windows Domain.
On the Android & iOS apps, you may set DNS servers manually to override the system DNS, or use the controller configured DNS which behaves the same as macOS & Windows in providing a DNS server for a specific search domain. If your particular flavor of Android sets it as a system-wide DNS server, then that may be an implementation-specific irregularity of your Android version; not our intention with our implementation of controller based DNS configuration.