All current Rally1 and Rally2 cars have heated windscreens. It's not any extra weight as heated/non heated windscreens weight difference is really not relevant. It's also basically 2m of extra wiring needed, so also not extra weight. And power is supplied anyway by power boxes, so no any extra fuses, etc.
All the cars have also quite efficient blowers. But there are certain conditions when those are not efficient enough, with so much water all around, cold outside temps, very warm inside temps, etc.
Sometimes the difference is made by the moment when you close your roof vent, or if the water goes inside by roof vent, etc, etc