From Wazeopedia

Background for dual red-light/speed cameras

The advice to set the speed on dual red-light/speed cameras to zero seems illogical. However, it is based on practical considerations. The current Waze implementation provides NO warning for a dual camera if the driver is not exceeding the speed limit. After extensive discussion we decided to follow the UK lead, and set the speed to zero so that drivers always receive a warning.

UK Country Manager iainhouse said on 4 Feb 2019 "Note that we have been asking Waze for a change in the way the app announces combined cameras for about 5 years now, without result. Ideally, we'd like combined cameras to announce themselves as such - but until we get a change, this is the best we can do."