I shave my head and my face 3 times a week. Last week though I let it grow for 5 days. Starting with day 3 there was dandruff all aover my scalp, especially on the sides. It's true, it was not the usual flaky dandruff, rather something like drying of the skin on the head. I also noticed my eyebrows have some white flakes in it, but nothing to be worried of.
In conclusion, whatever works for SD on the face has nothing to do with dandruff on the head. At least not for me.