If Doug Kent did not make the show and did not make the top 40, then Oatman would have been in 38th place, still making the cut for next year. Doug moving into the top 40 or staying out of the top 40 would not have changed who made the cut for next year.
If Kent is in top 40, cut line is 39th...oatman is 39th so he is exempt. if kent is out of the top 40, the cut line is 38th...oatman would have been 38th, and exempt.