Ender dragons' rotation value and visual rotation do not match, it is visually rotated 180 degrees.

Steps to reproduce:

• Spawn an ender dragon.

  /summon ender_dragon

Option 1:

• Run the following command in a repeating command block:

  /execute at @p as @e[type=ender_dragon] run tp @s ^ ^ ^20 facing ^ ^ ^-20

• Observe the dragon faces away from you.

Option 2:

• Run the following command in a repeating command block:

  /execute as @p at @e[type=ender_dragon] positioned ^ ^ ^10 facing entity @e[type=ender_dragon,limit=1] feet run tp @s ~ ~ ~

• Observe you're put behind the dragon

Option 3:

• Run the following command in a repeating command block:

  /execute as @p at @e[type=ender_dragon] run tp @s ~ ~ ~ ~ ~

• Observe you're facing the opposite direction from the dragon at all times.

The dragon faces the exact opposite direction, being visually rotated 180 degrees compared to the rotation value; this messes up commands which use the local coordinates.