That was quick. Cisco TAC have identified that CISCO-ENTITY-SENSOR-MIB:entSensorValue is reporting the correct sensor status of "1" for green/good. Based on conversation I've had with SolarWinds support it seems that Orion is using CISCO-ENTITY-SENSOR-MIB:entSensorThresholdSeverity which is not the actual status.
I've just contacted SolarWinds support again to confirm and to suggest they use entSensorValue if that is the case.