https://w3c.github.io/sensors/#concepts-sensors says

In simple cases, a platform sensor corresponds to a single device sensor, but if the provided sensor readings are a product of sensor fusion performed in software, the platform sensor corresponds to a set of device sensors involved in the sensor fusion process.

whereas https://w3c.github.io/sensors/#connect-to-sensor has

If the device has a single device sensor which can provide readings for type, then
[...]
If the device has multiple device sensors which can provide readings for type, then

which essentially assumes there is one device sensor backing a platform sensor.

The language needs to be adjusted so that multiple device sensors are accepted and processed accordingly (i.e. platformSensor remains null if connecting to all required sensors does not work).