If you kill the ender dragon using /kill @e it will not go to the center. When normally killing it the dragon even though dead will fly to the center portal area then die, but this is not the case for kill @e

Steps to reproduce 

1. Go to the end
2. Do /kill @e
3. Observe the dragon

Observed results: the dragon dies and drops xp in place

Expected results: the dragon will fly to the center and die