Outside of DC, Thomas is thought of as a righty platoon bat and a 4th outfielder. nothing more. In this lineup, he's viewed as a 1/2/4 prime bat.
In todays lineup Young is batting lead-off. I would have preferred Thomas to get his bat going. Im guessing that DM doesn't want to upset the apple cart as it will only be for a couple of fays with Abrams out.