A Bit of Puzzlement

I am truly puzzled.
Two or three years ago, a huge oak tree fell in the bottomland during a fierce windstorm. The bulk of it has been suspended off the ground for that entire time, resting at one end on its shattered and splintered trunk, and halfway down its length on the nub of a large branch that impaled the earth.

Some time ago I stripped much of the bark off it, and cut up the limbs for firewood. Last summer I sliced off a half a dozen or so lengths for seating around the firepit; this fall I split and stacked those for firewood. More recently, I cut more 16" slices, and split and stacked them to dry briefly in place. I have worked my way down the massive trunk to the point where my chainsaw will not quite sever the trunk when cutting from both sides, so it must be more than 32" in diameter.

What puzzles me is that much of this wood is still completely green (i.e., wet, unseasoned) after so much time; for all intents and purposes, it has not dried at since it fell. How can this be?

I recall hearing that for cut and split wood, you allow one month per inch of diameter; how can so little drying have taken place in a tree without roots, branches or leaves, that is completely surrounded by airflow?