This is mostly a guess but I would think that any hot/warm coolant going through the radiator would melt the snow slowly if the coolant is warm enough. The snow would provide cooling while that is happening. So my guess would be that snow being stuck there should not affect it much given that it the car is in a cold environment and thus cooling needs are reduced. Audi tested the e-tron quite extensively in hot and cold climates. If this was an issue, I would think they made an announcement or put something in the manual.