Keying rotation with quaternion interpolation can give unexpected results

Adding keys when quaternion interpolation is enabled can lead to unexpected results. 

1. Create a level sequence
2. Add a cube to the sequence 
3. Add a key to the cube's transform on the first frame
4. scrub forward a bit (e.g. 2 seconds)
5. Set the cube's Y (pitch) rotation to 270 degrees
6. Play back the sequence, notice it rotates from 0 to 270 not 0 to -90 degrees
7. Right click on the transform section and enable Quaternion Interpolation in its properties
8. Play back the sequence, notice it now rotations from 0 to -90 degrees
9. Scrub halfway between the two keys, and add a key for all rotations by pressing the add key button, without changing any values
10. Play back the sequence

RESULT

The cube rotations from 0 to 270 again.

EXPECTED

The path the cube rotated in would remain the same.