you would inevitably compact the snow on some spots on the wing and that the snow might get brushed into flight control hinges. Sounds acceptable to me as well!
Yes and that is the problem in the first place,snow into the flight control hinges.
If FINNAIR had a special procedures in case of weather colder than lets say -30c, why wasnt the captain made aware of it via fcom,safety bulletin or else.
Why did he have to rely on the maintenance supposely knowledge of deicing procedures?
I also flew from airports where snow accumulated.It was initially brushed off then 2 steps deicing was done within close distance of the holding point.(temp was below -20c),snow had accumulated mostly on the root area of the wing(easily 20cm).Two deicing trucks used to reduce deicing time.
I wouldnt have personally accepted the maintenaNce word unless clearly stated in a written form and under what circumstances.
I guess they would have had also a concern on their fuel temperature...