My thoughts exactly, if its rolled down too tight vs lightly patted down to form the swath that helps press the canola right to the ground and starts to mold and then sprout with prolonged wet. Also depends on how wide the swath is for the width of the swather header as a tight mass can't breath the same as a less dense swath or if the swath is bunchy vs a nice flow out of the swather. In the end you will only know when you go to combine it as to what the sample looks like and how ugly it looks under the swath. Having said that though, canola usually fairs much better then wheat and certainly better then sprouting barley in a swath.