In my experience it has nothing to do with the effect that Prednisone has on hormones, but the fact that it suppresses the immune system and therefore allows the acne causing bacteria to thrive.

I was on long term Lyme antibiotic therapy and all my acne went 100% away (I have always had acne before). After stopping the antibiotics the acne started coming back slowly and after prednisone the same type of acne got even worse.