Not quite.
Yes, quite. There may be a very, very few that react with some or other natural chemicals and change form, but the only thing fractionation does is separate them by density. The more important effect is to break up the large "blobs" into small ones. Smaller blobs to two things, allow more of those chemicals that might actually be soluble in water to dissolve, and increase the surface area available for bacteria to attach to, and start "eating" the oil.