In 8.6, Russian Units in the four hexes adjacent to Finland can attack.
I can see only 3 such hexes (Leningrad and 2 swamp hexes west of Lake Onega.
And, without having taken any one of these hexes, how can German send Units in Finland ?
Indeed, the map was slightly modified before the game release, so now there is only 3 adjacent hexes instead of 4, sorry about that.
The Germans cannot get to Finland besides from those 3 hexes.