Steps to reproduce:
Place an item frame with a compass in it on the side of a block
Summon an item display with a compass in it next to it, facing the same direction
Results:
The compass points the wrong way
If the display entity is rotated to face the Z axis (rotation 0 or 180) or the negative X axis (rotation 90), turning it around exactly 180 degrees makes it point the right way
If the display entity is rotated to face the positive X axis (rotation -90), it points wrong even when turned backwards
Expected results:
The compass in the display entity points the same way as the compass in the item frame and the one held in the player's hand
Can confirm.