All they needed to do was 'brush' the snow off the wing and thats de-icing complete = clean wing. Anti-icing wasn't necessary unless it is or is about to precipitate. Granted the airflow blew the snow off just like the brushing would but of course no guarantees.
However, if the pilots checked that the snow was not adhering to the wing AND there was no ice underneath AND their Ops Manual permitted this practice AND the Captain was satisfied that the wing would be 'clean' at lift-off then there is not really any problem.
In warmer climates we take-off with water on the wing all the time on the understanding that it blows off during the take-off run. I would be more than happy to apply the same premiss to non-adhering snow BUT my Company Ops Manual doesn't give me that degree of latitude.
I think the pilots of the former Soviet Union, Balkan and Scandinavian states are more used to extreme winter conditions than their southern european counterparts.