I have just been reading that some beekeepers will pour very fine granulated sugar into the brood box near the back wall of the hive (farthest from the entrance) , and just let it flow down thru the frames , some sits on the top bars , and some will stick to the comb on the way down , and some will flow down thru the bottom deep and end up on the bottom board.

I understand this will help feed some hives that will not come to the top for food during cold weather , it sounds feasible to me.

Are there any problems with this method that may be detrimental to the hive?

This is not regular sugar but "berry" sugar which is very fine , apparently the bees will use it instead of throwing it out of the hive.