If the topmost non-air block at coordinates (0, y, 0) is too far away from the ender dragon, the ender dragon does not fly towards (0, y, 0) if it's killed and instead immediately plays its death animation. If the dragon is close enough to the topmost block, it will first fly towards it, as explained in MC-207174, and then play its death animation.

How to reproduce:

1. Go to the End.
2. Execute the following command: 

   /fill 0 0 0 0 255 0 minecraft:bedrock

3. Execute the following command: 

   /damage @n[type=minecraft:ender_dragon] 10000 minecraft:player_attack by @s

Expected result:

The ender dragon would fly to the center of the world if killed regardless of any blocks placed there.

Observed result:

The ender dragon does not fly to the center of the world before playing its death animation if killed when too far away from the topmost center block