This final idea is similar to 2.f4 against the French, but this time you use it against the Caro-Kan. Black’s queen’s bishop isn’t shut in here but he has to lose a tempo in playing …c7-c6-c5 (an almost mandatory pawn advance). I’m not sure who this favours.
One big advantage of playing a little known opening like this is that it deprives one’s opponent of ready made solutions. The disadvantage is that we don’t have them either, so make sure you know how to improvise before giving them a whirl!
Here’s a 2.f4 game by Nigel Short in which his opponent loses his way on move 12.