Lou is right. Actually 30% is about perfect for haylage. The key point in the process is that you have to wrap it to eventually starve it of oxygen.
Once you bale, you've take all the moisture trapped inside and gave it an escape route. As it tries to perspire (ie. breakdown) its going to generate heat and being tight it retains it. Decomposition requires oxygen which generates heat. Get the oxygen out it turns into fermentation which will be lower in sugar than hay but more digestible.
I've had the same thoughts but mine was with frozen manure when cleaning out the paddock. Stuff frozen rock solid, put it in a pile compact it, never got above freezing and then rolled the pile and have steam billowing off it.
Thanks for your post btw. I read a few articles on frost baling but most were after first heavy frost not this late like yours. Are you just using it as filler feed?