GSX registers icing conditions at +8 or below,
No, it doesn't. The below +8 is the absolute limit for even considering possible icing but, when icing is above zero (and below +8 ), will be registered only in these cases:
- Dew point is within 2°C of temperature (high humidity)
- Dew point is higher than temperature (super saturated air)
- It's either raining/snowing
If the temperature is between 0 and +8, but none of the above is true, deicing won't be registered.