Well I used to change the oil before winter storage then I talked to an old school rider and he convinced me to change it in the spring instead. My bike is stored in a unit with no heat. He and others have since said the same thing. Over the course of the winter we have freeze thaw periods this creates condensation on the inside of the motor. during the thaw cycles this condensation collects and at times will run down and sit on the oil. Your not going to get anything substantial, (like a litre), but you are going to have water sitting on your oil. When you start it up in the spring what happens to that water? It becomes mixed with the oil. So the bike gets fresh oil in the spring before it is started and run.
What other voodoo black magic have you bought into? There won't be any condensation inside your motor because there is no air flow through your motor. If the bike was good and warm the last time you ran it beforw storage there will be very little moisture left inside the motor. None to condense on the inside of your crank case and contaminate your oil.