Just a guess, but I bet it's a Sky thing rather than BBBoC thing. Sky probably do it for scheduling reasons or something.
I can't give a reference because I can't put my hand on the book at the moment but fighting seasons have been around for at least a couple of hundred years when most organised fights took place in travelling, county and game fairs. The fair season was between October and August, with September off for the harvest, hence the season break. I will have a look tommorrow for the book in question so I can give a definitive reference.
Did Danny Williams finish top of the league now that the seasons finished? Or was that fight the cup final? Either way the ref had a shocker!